Polymer composition and uses thereof

ABSTRACT

The present invention concerns a polymer composition comprising: a block copolymer (a) including a polymer block A, which is composed mainly of an α-methylstyrene, and a hydrogenated or unhydrogenated polymer block B, which is composed of a conjugated diene or isobutylene and has a weight average molecular weight of 30,000 to 200,000; an acrylic resin (b); and a softener (c), 
     wherein proportions (by mass) of the respective components in the polymer composition are such that each of the following relationships (1) and (2) holds:
 
0.05 ≦Wb/Wa ≦2 and  (1)
 
 Wc /( Wa+Wb+Wc )≦0.5  (2)
 
wherein Wa, Wb, and Wc represent amounts (by mass) of the block copolymer (a), the acrylic resin (b) and the softener (c), respectively.
 
     The polymer composition obtainable in accordance with the present invention is favorable in terms of such physical properties as formability, scratch resistance, abrasion resistance, flexibility, mechanical strength, rubber elasticity, and transparency and exhibits these properties in a well-balanced manner. By exploiting these favorable properties, the polymer composition can be effectively used in a wide range of applications, including stretchable materials, laminates, and foams.

TECHNICAL FIELD

The present invention relates to a polymer composition that contains athermoplastic elastomer in the form of a block copolymer. In the polymercomposition, the block copolymer contains as its hard segment a polymerblock composed mainly of α-methylstyrene. The present invention alsorelates to use of such polymer compositions. The polymer composition ofthe present invention is useful not only in terms of such properties asformability, flexibility, rubber elasticity, mechanical strength, andtransparency, but also especially in terms of scratch resistance andabrasion resistance. These characteristics together make the polymercomposition suitable for use in stretchable materials, laminates, foams,and various other applications.

For example, the stretchable materials using the composition of thepresent invention exhibit, aside from the above-describedcharacteristics, a high stress relaxation property (stress retention)and a low tensile permanent set, as well as good extensioncharacteristics, including extension stress. Such a stretchable materialenables formation of thin film and a reduction in Metsuke, leading to acost reduction and a saving of resources.

Also, the laminates in which a layer, especially the outermost layer, isformed of the polymer composition of the present invention can beeffectively used in applications where properties such as scratchresistance, abrasion resistance, and flexibility are required.

In addition, a foam composition can be prepared by adding apredetermined proportion of a blowing agent to the polymer compositionof the present invention. A foam obtained by foaming such a compositioncan be effectively used in applications where properties such aslightweight, heat resistance (e.g., compression permanent set at 70°C.), scratch resistance, abrasion resistance, flexibility, andformability are required.

BACKGROUND ART

Thermoplastic elastomers show rubber elasticity at room temperature andare easy to mold since they are readily plasticized, or melt, whenheated. Also, these materials are recyclable. Because of theseadvantages, thermoplastic elastomers have recently become widely used inautomobile parts, parts for home electric appliances, constructionmaterials, toys, sports equipment, daily necessities, and various otherapplications. They are also used as stretchable materials in sanitaryproducts, medical materials, belt materials, and other miscellaneousitems.

Of different thermoplastic elastomers, polyurethane-based thermoplasticelastomers are most widely used as stretchable materials because oftheir good extension stress and good stress relaxation property.Styrene-based thermoplastic elastomers, such asstyrene-butadiene-styrene block copolymers (SBS),styrene-isoprene-styrene block copolymers (SIS), and hydrogenatedproducts thereof, are also widely used because of their cost efficiency,flexibility, rubber elasticity, and recyclability.

As for the styrene-based thermoplastic elastomers, attempts have beenmade to improve different physical properties. The results of suchattempts include: <1> a thermoplastic elastomer resin composition forpowder molding that contains a styrene-based thermoplastic elastomer, apolyurethane-based thermoplastic elastomer and other components andwhich can be used to make molded articles that have a soft texture and ahigh scratch resistance (See, Japanese Patent Laid-Open Publication No.2001-158812); and <2> a thermoplastic elastomer composition thatprovides a high flexibility, high formability, and high scratchresistance and that comprises a composition consisting of astyrene-based thermoplastic elastomer (hydrogenated block copolymer) anda methacrylic resin, and a copolymer comprising units that arecompatible to the two components of the composition (See, JapanesePatent Laid-Open Publication No. Hei 5-230322).

Also proposed are thermoplastic resin compositions that have flexibilityand provide a low temperature performance while preserving favorableproperties of acrylic resins, including surface properties such assurface hardness, weather resistance, and clear appearance. Among suchthermoplastic resin compositions are <3> an acrylic thermoplastic resincomposition containing, at a predetermined ratio, a hydrogenated productof a block copolymer that contains a polymer block (a) composed of anaromatic vinyl compound having a predetermined molecular weight and apolymer block (b) composed either of isoprene and a mixture of isopreneand butadiene; and an acrylic resin having a predetermined intrinsicviscosity (See, Japanese Patent Laid-Open Publication No. Hei 6-329865);and <4> a thermoplastic resin composition containing at a predeterminedratio an acrylic resin and a hydrogenated product of a triblockcopolymer that has an a-b-a structure (where “a” is a block composed ofan aromatic vinyl compound; and “b” is a block composed of isopreneand/or butadiene) and has a predetermined number average molecularweight (See, Japanese Patent Laid-Open Publication No. Hei 5-295216).

Compositions that can provide a high flexibility and high weatherresistance while offering a favorable appearance are also proposed. Oneexample is <5> a thermoplastic resin composition comprising a polyolefinresin (A); a hydrogenated product of a thermoplastic block copolymer(B), composed of a block composed of an aromatic vinyl compound and ablock composed of isoprene and/or butadiene; an acrylic resin (C); ahydrocarbon-based softener (D); and a hydrogenated product of athermoplastic block copolymer (E), composed of a block composed of anaromatic vinyl compound having a side chain of polymerized acrylicmonomer and a block composed of isoprene and/or butadiene (See, JapanesePatent Laid-Open Publication No. Hei 5-345841). Also, <6> an adhesivetape is disclosed that has a sufficient tensile strength and a properlylow tear strength. This adhesive tape includes a substrate formed of acomposition that contains at a predetermined ratio an acrylic polymercomposed mainly of a methyl methacrylate; and a hydrogenated product ofa block copolymer, including a polymer block composed of an aromaticvinyl compound and a polymer block composed of isoprene and/or butadiene(See, Japanese Patent Laid-Open Publication No. 2000-303037).

The composition <1> described above has a somewhat improved scratchresistance, though not as high as that of polyurethane-basedthermoplastic elastomers. Nevertheless, this composition, lackingrequired hydrolysis resistance and weather resistance, poses problemssuch as decrease in performance and yellow discoloration when formedinto molded articles. Each of the compositions <2> through <5> describedabove is highly flexible and has high formability and transparency whileretaining surface properties, such as surface hardness, weatherresistance, and clear appearance, each of which is inherent to acrylicresins. As for the composition <2>, the scratch resistance was evaluatedaccording to JIS Z 8741 in which test samples were rubbed 100 times witha piece of cloth (Kanakin No. 3) while applying a load of 500 g and theglossiness of the sample surface remaining after the test was comparedwith the initial glossiness of the sample. For the compositions <3> to<5>, the pencil scratch resistance was evaluated according to JIS K5400. However, none of the compositions <3> to <5> had proven to havesufficient scratch resistance or abrasion resistance. For thecomposition <6>, nothing is mentioned concerning the abrasion resistanceof the composition. Under such circumstances, a need exists for athermoplastic polymer composition that is suitable for use inapplications where it is expected to be subjected to frequent frictionor in applications where aesthetic appearance is important.

In regard of the styrene-based thermoplastic elastomers, severalproposals have been made with the aim of improving extensioncharacteristics, including formability and extension stress, ofstretchable materials formed of the styrene-based thermoplasticelastomers. One example is <7> a stretchable nonwoven fabric describedin Japanese Patent Laid-Open Publication No. Hei 3-130448, which showssuperior extension characteristics (e.g., stretch and stretch recovery),high strength (e.g., water pressure resistance), and good lightresistance and has a soft texture. The stretchable nonwoven fabric ismade of a fiber, which comprises a hydrogenated block copolymerobtainable by hydrogenating a block copolymer that includes at least twopolymer blocks A composed mainly of an aromatic vinyl compound and atleast two polymer blocks B composed mainly of a conjugated dienecompound, and a polyolefin. The hydrogenated block copolymer and thepolyolefin are mixed at a predetermined weight ratio. The nonwovenfabric is made of ultrafine fiber with an average fiber size of 10 μm orless. Another example is <8> a stretchable nonwoven fabric described inJapanese Patent Laid-Open Publication No. Hei 2-259151, which hassuperior extension characteristics. The stretchable nonwoven fabriccomprises a thermoplastic fiber made of a hydrogenated product of ablock copolymer that includes at least two polymer blocks A composedmainly of an aromatic vinyl compound and at least two polymer blocks Bcomposed mainly of a conjugated diene compound with at least one of thepolymer blocks B being situated at one end of the polymer chain. Thenumber average molecular weight of the hydrogenated product and theamount of the aromatic vinyl compound are within specific ranges. Stillanother example is <9> a stretchable nonwoven fabric described inJapanese Patent Laid-Open Publication No. Sho 63-203857 that shows agood extension recovery, flexibility, and light resistance. Thisstretchable nonwoven fabric is made of a thermoplastic polymercomposition that contains a thermoplastic polymer (a) having a polarfunctional group, such as polyamide and polyester; and a modified blockcopolymer and/or a modified block-graft copolymer (b) in which a blockcopolymer consisting of an aromatic vinyl compound polymer block and aconjugated diene compound polymer block and/or a hydrogenated productthereof, or a block-graft copolymer in which the copolymer serves as thebackbone and a radically decaying polymer serves as the grafts, arebound to a molecular unit having a functional group capable of bingingto, or interacting with, the thermoplastic polymer (a) (e.g., maleicanhydride group).

While polyurethane-based thermoplastic elastomers are favorable in termsof formability, stress relaxation property, and extension stress, theirhydrolysis resistance and weather resistance are poor, often resultingin a significant reduction in performance or yellow discoloration. Also,each of the stretchable materials <7> to <9> described above is notsatisfactory as far as the balance among formability, stress relaxationproperty, tensile permanent set, and extension stress is concerned.

To impart additional functions to materials such as resin to be used asa substrate, a plurality of materials are laminated on top of oneanother. Such laminates are used in a variety of fields, includingautomobile parts, parts for home electric appliances, constructionmaterials, furniture, toys, sports equipment, and daily necessaries.

Soft vinyl chloride resins are inexpensive materials and have superiorsurface characteristics, such as scratch resistance and abrasionresistance, as well as flexibility. For this reason, these resins arepreferred materials for use in the above-described laminates, especiallyin the outermost layer of the laminates. Nevertheless, soft vinylchloride resins have several drawbacks: plasticizers contained in theresins seep out; such plasticizers are potential endocrine disruptors;and the resins generate corrosive gases, such as hydrogen chloride, andhighly toxic dioxins when incinerated.

Olefin-based thermoplastic elastomers, styrene-based thermoplasticelastomers, and polyurethane-based thermoplastic elastomers each havesuperior surface characteristics, such as high scratch resistance andhigh abrasion resistance, as well as flexibility, and can thus be usedto form laminates. In particular, olefin-based thermoplastic elastomers,which are favorable in terms of strength and cost, and styrene-basedthermoplastic elastomers, which are favorable in terms of mechanicalproperties and flexibility, do not pose the problems associated with thesoft vinyl chloride resins and are considered as an alternative to thesoft vinyl chloride resin. Laminates using these materials have beenproposed (See, for example, Japanese Patent Laid-Open Publications No.Hei 4-73112, No. Hei 4-73142, and No. Hei 8-90723). Also, <10> a methodis described by which a surface layer composed mainly of apolyurethane-based thermoplastic elastomer, an adhesive resin layer, anda substrate layer or a foam layer composed mainly of a thermoplasticresin are coextruded to form a sheet-like laminate (See, for example,Japanese Patent Laid-Open Publications No. Hei 7-68623 and No Hei7-290625). <11> A laminate described in Japanese Patent Laid-OpenPublication No. Hei 6-8381 comprises (i) a thermoplastic resin layer;and (ii) a layer formed of a composition obtained by adding apredetermined amount of a hydrogenated product of a thermoplastic blockcopolymer, the thermoplastic block copolymer having a polymerizedacrylic monomer side chain and consisting of a block composed of anaromatic vinyl compound and a block composed of isoprene and/orbutadiene, to 100 parts by mass of a predetermined mixture of an acrylicresin and a hydrogenated product of a thermoplastic block copolymercomposed of a block composed of an aromatic vinyl compound and a blockcomposed of isoprene and/or butadiene.

However, nothing is mentioned about the scratch resistance or theabrasion resistance of the outermost layers of the laminates in any ofJapanese Patent Laid-Open Publications No. Hei 4-73112, No. Hei 4-73142,and No. Hei 8-90723. In regard of the laminate <10> described above,when olefin-based materials are used in the substrate layer of thelaminate, an adhesive resin layer must be provided to adhere thesubstrate layer. This adds to the complexity of the production process.The laminate <10> also has a problem that the insufficient hydrolysisresistance and the insufficient weather resistance of thepolyurethane-based thermoplastic elastomer may cause a reduction in theperformance. While the laminate <11> as described above is favorable interms of flexibility, weather resistance, appearance-related properties,and adhesion, nothing is mentioned about the scratch resistance or theabrasion resistance of the laminate.

Various foams that make use of styrene-based thermoplastic elastomershave been proposed for the purposes of reducing weight and providingcushioning property. Among such foams are <12> an extruded foam articleusing a composition composed of a styrene-based thermoplastic elastomerhaving a predetermined melt tension, melt malleability, hardness(JIS-A), and melt flow rate (MFR), and a blowing agent (See, JapanesePatent Laid-Open Publication No. Hei 7-18106); <13> a expandablethermoplastic elastomer composition, comprising a block copolymercomposed of at least two polymer blocks A formed mainly of an aromaticvinyl compound and at least one polymer block B formed mainly of aconjugated diene, and/or a hydrogenated product thereof; aperoxide-degradable olefin-based resin and/or a copolymer rubbercontaining the same; a polyethylene-based resin polymerized by asingle-site catalyst; a softener for non-aromatic rubbers; and aheat-expandable microcapsule that expands at a temperature of 100° C. to200° C. (See, Japanese Patent Laid-Open Publication No. 2000-17140); and<14> a thermoplastic polymer foam, obtainable by foaming a thermoplasticpolymer composition containing a thermoplastic acrylic polymer and ahydrogenated block copolymer at a weight ratio of 80:20 to 20:80, thehydrogenated block copolymer containing a polymer block composed of anaromatic vinyl compound and a polymer block composed of a conjugateddiene (See, Japanese Patent Laid-Open Publication No. Hei 9-241414).

The foam article <12> has a superior molded appearance, flexibility, andlow-temperature impact resistance, and the expansion ratio of the foamarticle is high. The expandable thermoplastic elastomer composition <13>can form articles with a favorable appearance and texture even when theexpansion ratio is considerably high. Finally, the thermoplastic polymerfoam <14> is highly flexible and retains the flexibility at lowtemperatures. Since this material does not contain any plasticizers, itdoes not pose problems such as the plasticizer seeping out or beingtransferred. Nonetheless, nothing is mentioned concerning the scratchresistance or the abrasion resistance for any of the foams <12> to <14>,nor can any teaching be found in the respective publications regardingthe production of foams that have a good heat resistance, in particular,regarding the production of those that exhibit a superior compressionpermanent set at high temperature (e.g., at 70° C.). Thus, a need existsfor a foam that is suitable for use in applications where it is expectedto be subjected to frequent friction or high temperature conditions.

Accordingly, it is an object of the present invention to provide apolymer composition that has a high formability, flexibility, rubberelasticity, mechanical strength, and transparency while exhibiting ascratch resistance and abrasion resistance comparable to those ofpolyurethane-based thermoplastic elastomers and polyester-basedthermoplastic elastomers. By exploiting these characteristics, suchpolymer compositions can be effectively used in a wide range ofapplications, including stretchable materials, laminates, and foams.

It is another object of the present invention to provide a stretchablematerial that does not pose any of the above-identified problemsassociated with conventional stretchable materials and is formed of apolymer composition that provides a good flexibility, rubber elasticity,mechanical strength, and stress relaxation property while exhibiting aminimum tensile permanent set and being readily formed. This stretchablematerial exhibits superior extension characteristics, includingextension stress.

It is a further object of the present invention to provide a laminatecomprising a layer formed of a polymer composition that has a highscratch resistance, abrasion resistance, and flexibility and can readilybe manufactured without requiring complicated processes.

It is a still further object of the present invention to provide a foamthat not only shows a high heat resistance, in particular highcompression permanent set at a high temperature (e.g., at 70° C.), butalso an scratch resistance and abrasion resistance comparable to thoseof polyurethane-based thermoplastic elastomers, while preservingcharacteristics of styrene-based thermoplastic elastomers, includingflexibility and formability. It is also an object of the presentinvention to provide a foam composition for forming such a foam.

In an effort to find ways to attain the above-described objects, thepresent inventors have found that by providing a specific polymercomposition that contains a block copolymer having a molecular weight ina predetermined range and containing a block composed mainly ofα-methylstyrene as its hard segment, an acrylic resin, and an optionalsoftener, and by adjusting the ratio of these components of the polymercomposition, the block copolymer containing a block composed mainly ofα-methylstyrene as its hard segment forms a continuous phase (i.e.,matrix) and the acrylic resin disperses throughout the block copolymer,forming a specific sea-island morphology.

The present inventors examined the physical properties both of thispolymer composition having the above-described specific morphology andof molded articles formed of the polymer composition and have found thatsuch polymer compositions show a high formability, exhibit many otherfavorable characteristics, including flexibility, rubber elasticity,mechanical strength, transparency, and, above all, scratch resistanceand abrasion resistance, exhibit these properties in a well-balancedmanner, and are therefore suitable for use in a wide range ofapplications.

For example, the present inventors have found that a stretchablematerial formed of the polymer composition shows a good stressrelaxation property, a small tensile permanent set, as well as superiorextension characteristics, including extension stress, and can thus beeffectively used in various fields including hygiene products, medicalmaterials and other miscellaneous goods.

The present inventors have also found that a laminate comprising a layerformed of the polymer composition and a layer formed of other materials,preferably, a layer formed of a thermoplastic resin such as anolefin-based resin, olefin-based thermoplastic elastomer, styrene-basedthermoplastic elastomer, or a resin composition containing styrene-basedthermoplastic elastomer, shows a high scratch resistance, abrasionresistance, and flexibility and can be effectively used in a wide rangeof applications by exploiting these characteristics.

The present inventors have further found that by adding a predeterminedamount of a blowing agent to the polymer composition so as to reduceweight and provide an cushioning property, a foam composition can beobtained that can be foamed into a foam with a good foamability and heatresistance, in particular, a good compression permanent set at a hightemperature (e.g., at 70° C.) and that such a foam can be effectivelyused in a wide range of applications. These findings led the presentinventors to devise the present invention.

DISCLOSURE OF THE INVENTION

Accordingly, the present invention provides:

[1] a polymer composition comprising:

-   -   a block copolymer (a) including a polymer block A, which is        composed mainly of α-methylstyrene, and a hydrogenated or        unhydrogenated polymer block B, which is composed of a        conjugated diene or isobutylene and has a weight average        molecular weight of 30,000 to 200,000;    -   an acrylic resin (b); and    -   a softener (c),        wherein proportions (by mass) of the respective components in        the polymer composition are such that each of the following        relationships (1) and (2) holds:        0.05≦Wb/Wa≦2  (1) and        Wc/(Wa+Wb+Wc)≦0.5  (2)        wherein Wa, Wb, and Wc represent the amounts (by mass) of the        block copolymer (a), the acrylic resin (b), and the softener        (c), respectively.

The present invention also provides:

[2] a stretchable material formed of the polymer composition accordingto [1] above; and

[3] a laminate comprising a layer formed of the polymer compositionaccording to [1] above and a layer formed of a different material.

The present invention further provides:

[4] a foam composition comprising: the polymer composition according to[1] above and a blowing agent (d) being contained in a proportion (bymass) that the following relationship (3) holds:0.01≦Wd/(Wa+Wb+Wc)≦0.1  (3)wherein Wa, Wb, Wc, and Wd represent the amounts (by mass) of the blockcopolymer (a), the acrylic resin (b), the softener (c), and the blowingagent (d) that together form the foam composition, respectively.

Finally, the present invention provides:

[5] a foam obtained by foaming the foam composition according to [4]above.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention will now be described in detail.

The block copolymer (a) for use in the polymer composition of thepresent invention is a block copolymer that includes a polymer block A,which is composed mainly of α-methylstyrene, and a hydrogenated orunhydrogenated polymer block B, which is composed of a conjugated dieneor isobutylene. The block copolymer (a) has a weight average molecularweight of 30,000 to 200,000. While the polymer block A of the blockcopolymer (a) is preferably composed solely of structural units derivedfrom α-methylstyrene, the polymer block A may contain a small amount,preferably 10% by mass or less relative to the polymer block A, of oneor two or more of structural units derived from unsaturated monomersother than α-methylstyrene, such as butadiene, isoprene,2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 1,3-hexadiene, isobutylene,styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,p-t-butylstyrene, 2,4-dimethylstyrene, vinylnaphthalene,vinylanthracene, methyl methacrylate, methyl vinyl ether,N-vinylcarbazole, β-pinene, 8,9-p-menthene, dipentene, methylenenorbornene, and 2-methylene tetrahydrofuran, as long as these componentsdo not interfere with any of the objects and advantages of the presentinvention.

The amount of the polymer block A in the block copolymer (a) ispreferably in the range of 5 to 45% by mass, and more preferably in therange of 15 to 40% by mass, to ensure the rubber elasticity and theflexibility of molded articles or layers formed of the polymercomposition; the stress relaxation property and the tensile permanentset of stretchable materials made of the polymer composition; and theexpansion ratio, the heat resistance (e.g., compression permanent set at70° C.) and the flexibility of foams made of the foam compositionobtained by adding a predetermined amount of the blowing agent to thepolymer composition. The amount of the polymer block A in the blockcopolymer (a) can be determined, for example, by using ¹H-NMRspectrography.

The polymer block B in the block copolymer (a) is composed of aconjugated diene or isobutylene and may or may not be hydrogenated.Examples of the conjugated diene that composes the polymer block Binclude butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene,and 1,3-hexadiene. These conjugated dienes may be used eitherindividually or in combination of two or more to form the polymer blockB. Of the conjugated dienes for forming the polymer block B, preferredare butadiene, isoprene, mixtures of butadiene and isoprene, andisobutylene.

When the polymer block B is composed of a conjugated diene, thestructural units may be any microstructure derived from the conjugateddiene. However, when the polymer block B is composed of, for example,butadiene, the proportion of 1,2-linkages in the polymer block B ispreferably from 5 to 90 mol %, and more preferably from 20 to 70 mol %.Also, when the polymer block B is composed of either isoprene or amixture of butadiene and isoprene, the total proportion of 1,2-linkagesand 3,4-linkages in the polymer block B is preferably from 5 to 80 mol%, and more preferably from 10 to 60 mol %.

When the polymer block B is composed of two or more conjugated dienes(e.g., butadiene and isoprene), the structural units may be linked viaany type of linkage. For example, the conjugated diene units may belinked to one another in a random, tapered, or completely alternatingmanner or they may be linked to form partial blocks or blocks. Two ormore of the different types of linkage may be combined to form thepolymer block B.

When the polymer block B is composed of a conjugated diene, preferably50 mol % or more, more preferably 70 mol % or more, and even morepreferably 90 mol % or more of the carbon-carbon double bondsoriginating from conjugated diene units are hydrogenated to ensure heatresistance and weather resistance.

The degree of hydrogenation can be determined by measuring the amount ofcarbon-carbon double bonds originating from the conjugated diene unitsin the polymer block B before and after the hydrogenation process byusing the iodine number method, IR spectroscopy, and ¹H-NMRspectroscopy, and comparing the measurements obtained.

The polymer block B is composed of either conjugated diene orisobutylene and may or may not be hydrogenated. The polymer block B maycontain a small amount, preferably 10% by mass relative to the polymerblock B, of at least one structural unit derived from other unsaturatedmonomers such as styrene, α-methylstyrene, o-methylstyrene,m-methylstyrene, p-methylstyrene, p-t-butylstyrene, 2,4-dimethylstyrene,vinylnaphthalene, vinylanthracene, methyl methacrylate, methyl vinylether, N-vinylcarbazole, β-pinene, 8,9-p-menthene, dipentene, methylenenorbornene, and 2-methylene tetrahydrofuran, as long as these componentsdo not interfere with any of the objects and advantages of the presentinvention.

In the block copolymer (a), the polymer block A and the polymer block Bmay be linked via any type of linkage as long as the two types of blocksare linked to one another. For example, the two types of blocks may belinked in a straight-chained, branched, or radial manner, or two or morelinkages may be present in combination, although the polymer block A andthe polymer block B are preferably linked to form a straight chain.Examples of the straight-chained block copolymer include triblockcopolymers shown as A-B-A, tetrablock copolymers shown as A-B-A-B, andpentablock copolymers shown as A-B-A-B-A, given that “A” indicates thepolymer block A and “B” indicates the polymer block B. Of these,triblock copolymers A-B-A are preferred in terms of their readiness tomanufacture and the flexibility of the block copolymer (a).

It is necessary that the weight average molecular weight of the blockcopolymer (a) fall in the range of 30,000 to 200,000: The blockcopolymer preferably has an weight average molecular weight in the rangeof 35,000 to 180,000, and more preferably in the range of 50,000 to150,000. If the weight average molecular weight of the block copolymer(a) is less than 30,000, then the mechanical strength of molded articlesor stretchable materials formed of the polymer composition is reduced,as are the scratch resistance and the abrasion resistance of moldedarticles or layers formed of the polymer composition and the heatresistance (e.g., compression permanent set at 70° C.) of the foamcomposition obtained by adding a predetermined amount of a blowing agentto the polymer composition and foams obtained therefrom. On the otherhand, if the weight average molecular weight of the block copolymer (a)is greater than 200,000, then the formability of the polymer compositionand the scratch resistance and the abrasion resistance of moldedarticles and layers formed of the polymer composition are reduced, asare the stress relaxation property and the tensile permanent set ofstretchable materials formed of the polymer composition, the formabilityof the foam composition obtained by adding a predetermined amount of ablowing agent to the polymer composition, and the scratch resistance andthe abrasion resistance of foams obtained from the foam composition.

The term “weight average molecular weight” as used herein refers to aweight average molecular weight as determined by the gel permeationchromatography (GPC) using polystyrene standard.

The block copolymer (a) may include within, or at ends of, its moleculeone or two or more functional groups, such as carboxyl group, hydroxylgroup, acid anhydride group, amino group, and epoxy group, provided thatsuch functional groups do not interfere with the objects of the presentinvention. Those block copolymers (a) having functional groups may bemixed with those without functional groups.

The block copolymer (a) can be synthesized by using an anionicpolymerization technique. The following specific procedures are known:(1) Using a dianionic initiator such as1,4-dilithio-1,1,4,4-tetraphenylbutane, a conjugated diene ispolymerized in a tetrahydrofuran solvent. Subsequently, α-methylstyreneis sequentially polymerized at −78° C. to obtain a triblock copolymershown as A-B-A (Macromolecules 2 (1969): 453-58); (2) Using an anionicpolymerization initiator such as sec-butyllithium, α-methylstyrene ispolymerized in a non-polar solvent such as cyclohexane. Subsequently; aconjugated diene is polymerized, which is followed by addition of acoupling agent such as tetrachlorosilane and diphenyldichlorosilane(α,α′-dichloro-p-xylene or phenyl benzoate may also be used) to carryout a coupling reaction to obtain a block copolymer of (A-B)nX type(Kautschuk Gummi Kunststoffe 37 (1984): 377-79; and Polym. Bull. 12(1984): 71-77); (3) Using an organolithium compound as an initiator,α-methylstyrene at a concentration of 5 to 50% by mass is polymerized ata temperature of −30 to 30° C. in a non-polar solvent in the presence ofa 0.1 to 10% polar compound (by mass). A conjugated diene is polymerizedwith the resultant living polymer, followed by addition of a couplingagent to obtain a block copolymer shown as A-B-A; and (4) Using anorganolithium compound as an initiator, α-methylstyrene at aconcentration of 5 to 50% by mass is polymerized at a temperature of −30to 30° C. in a non-polar solvent in the presence of a 0.1 to 10% polarcompound (by mass). A conjugated diene is polymerized with the resultantliving polymer. Subsequently, the resulting living polymer, which is ablock copolymer composed of α-methylstyrene polymer block and aconjugated diene polymer block, is polymerized with an anionicpolymerization monomer other than α-methylstyrene to obtain a blockcopolymer shown as A-B-C.

Of the above-described specific production processes of the blockcopolymer, the processes (3) and (4) are preferred, with the process (3)being more preferred. These processes are described more specificallyhereinbelow.

Examples of the organolithium compounds for use in the above-describedprocesses include monolithium compounds such as n-butyllithium,sec-butyllithium and tert-butyllithium, and dilithium compounds such astetraethylenedilithium. These compounds may be used either individuallyor as a mixture of two or more.

The solvent used during polymerization of α-methylstyrene is a non-polarsolvent. Examples include aliphatic hydrocarbons such as cyclohexane,methylcyclohexane, n-hexane and n-heptane, and aromatic hydrocarbonssuch as benzene, toluene and xylene. These non-polar solvents may beused either individually or as a mixture of two or more.

The polar compound used during polymerization of α-methylstyrene is acompound that does not have any functional groups reactive with anionspecies (e.g., hydroxyl group and carbonyl group) and contains withinits molecule an oxygen atom, a nitrogen atom and a different heteroatom. Examples of such polar compounds include diethyl ether, monoglyme,tetramethylethylenediamine, dimethoxyethane and tetrahydrofuran. Thesepolar compounds may be used either individually or as a mixture of twoor more.

In order to ensure high conversion rate of α-methylstyrene duringpolymerization and to thereby control the amount of 1,4-linkages in theconjugated diene polymer blocks during subsequent polymerization ofconjugated diene, the concentration of the polar compound in thereaction system is preferably in the range of 0.1 to 10% by mass, andmore preferably in the range of 0.5 to 3% by mass.

In order to ensure high conversion rate of α-methylstyrene and to ensureviscosity of the reaction mixture during the late stage of thepolymerization, the concentration of α-methylstyrene in the reactionsystem is preferably in the range of 5 to 50% by mass, and morepreferably in the range of 25 to 40% by mass.

The term “conversion rate” as used herein refers to a proportion ofα-methylstyrene that has been converted to the block copolymer throughpolymerization. According to the present invention, the conversion rateis preferably 70% or higher, and more preferably 85% or higher.

Polymerization of α-methylstyrene is preferably carried out at atemperature in the range of −30 to 30° C., more preferably in the rangeof −20 to 10° C., and still more preferably in the range of −15 to 0°C., in view of the ceiling temperature of α-methylstyrene (a temperatureat which polymerization reaches equilibrium and no longer proceeds anyfurther), the rate of polymerization and the living property ofα-methylstyrene. By carrying out the polymerization at temperatureslower than 30° C., not only can a high conversion rate ofα-methylstyrene be ensured during polymerization, but the amount of theliving polymer that is deactivated can also be minimized, as can thecontamination of the resulting block copolymer withhomopoly-α-methylstyrene. As a result, physical properties of the blockcopolymer are not affected. Also, by carrying out the polymerization attemperatures higher than −30° C., the reaction mixture remains lessviscous, so that it can be stirred during the late stage of thepolymerization of α-methylstyrene. The polymerization reaction in thistemperature range is also economically favorable since the cost requiredto maintain the low temperature is relatively small.

In the above-described processes, a different aromatic vinyl compoundmay be added during the polymerization of α-methylstyrene, as long as itdoes not affect the properties of the α-methylstyrene polymer block, sothat it can copolymerize with α-methylstyrene. Examples of such aromaticvinyl compounds include styrene, o-methylstyrene, m-methylstyrene,p-methylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, andvinylanthracene. These aromatic vinyl compounds may be used eitherindividually or as a mixture of two or more.

Living poly-α-methylstyryllithium is produced through 0.5 polymerizationof α-methylstyrene using an organolithium compound as an initiator. Aconjugated diene is then polymerized with the resultingpoly-α-methylstyryllithium. Examples of such conjugated dienes includebutadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, and1,3-hexadiene. These conjugated dienes may be used either individuallyor as a mixture of two or more. Of the different conjugated dienes,butadiene and isoprene are preferred and may be used as a mixture.

For polymerization, the conjugated diene is added to the reactionsystem. The addition of the conjugated diene may be carried out by anysuitable method. For example, it may be added directly to the livingpoly-α-methylstyryllithium solution or it may be diluted with a solventbefore addition to the system. The conjugated diene can be diluted witha solvent and introduced into the reaction system by any of thefollowing manners: it may be diluted with the solvent after addition tothe reaction system; it may be added to the reaction system along withthe solvent; or it may be added to the reaction system after dilutionwith the solvent. In a recommended method, 1 to 100 molar equivalents,preferably 5 to 50 molar equivalents of the conjugated diene relative tothe living α-methylstyryllithium are first added to the reaction systemfor polymerization to form a conjugated diene block (which may bereferred to as polymer block b1, hereinafter) and to thus convert theliving active terminal. A solvent is then added to dilute the reactionsystem. Subsequently, the remainder of the conjugated diene is added andpolymerization is carried out at temperatures above 30° C., preferablyat temperatures in the range of 40 to 80° C., to form an additionalconjugated diene block (which may be referred to as polymer block b2,hereinafter). Instead of using a conjugated diene to convert the activeterminal of living poly-α-methylstyryllithium, an aromatic vinylcompound may be used such as styrene, o-methylstyrene, m-methylstyrene,p-methylstyrene, 2,4-dimethylstyrene, vinylnaphthalene, vinylanthracene,and 1,1-diphenylethylene.

Examples of the solvent that can be used in the above-described dilutionprocess include aliphatic hydrocarbons such as cyclohexane,methylcylclohexane, n-hexane and n-heptane, and aromatic hydrocarbonssuch as benzene, toluene and xylene. These solvents may be used eitherindividually or as a mixture of two or more.

A triblock or radial teleblock copolymer (a) can be produced byreacting, for example, a polyfunctional coupling agent with a livingpolymer of the block copolymer composed of conjugated diene polymerblocks and the α-methylstyrene polymer blocks obtained throughcopolymerization of living poly-α-methylstyryllithium and a conjugateddiene. The block copolymer used for this purpose may be a mixture thatcontains a desired proportion of a diblock, triblock, or radialteleblock copolymer obtained by adjusting the amount of thepolyfunctional coupling agent used. Examples of the polyfunctionalcoupling agents include phenyl benzoate, methyl benzoate, ethylbenzoate, ethyl acetate, methyl acetate, methyl pivalate, phenylpivalate, ethyl pivalate, α,α′-dichloro-o-xylene,α,α′-dichloro-m-xylene, α,α′-dichloro-p-xylene, bis(chloromethyl)ether,dibromomethane, diiodomethane, dimethyl phthalate,dichlorodimethylsilane, dichlorodiphenylsilane, trichloromethylsilane,tetrachlorosilane, and divinylbenzene. The amount of polyfunctionalcoupling agent is not strictly limited and can be properly adjusteddepending on the weight average molecular weight of the block copolymer(a). In order to hydrogenate the triblock or radial teleblock copolymer(a), which is obtained by reacting the polyfunctional coupling agentwith a living polymer of the block copolymer composed of theα-methylstyrene polymer blocks and conjugated diene polymer blocks, thecoupling reaction is terminated by adding, if necessary, an activehydrogen compound such as an alcohol, carboxylic acid and water, and theblock copolymer is then hydrogenated in an inert organic solvent in thepresence of a hydrogenation catalyst using a known process describebelow. This gives the hydrogenated block copolymer (a).

In comparison, in order to hydrogenate the block copolymer (a) composedof α-methylstyrene polymer blocks and conjugated diene polymer blocks, aconjugated diene is first polymerized with the livingpoly-α-methylstyryllithium and the polymerization is then terminated byadding an active hydrogen compound such as an alcohol, carboxylic acidand water, and the resultant copolymer is hydrogenated in an inertorganic solvent in the presence of a hydrogenation catalyst using aknown process described below. This gives the hydrogenated blockcopolymer (a).

The unhydrogenated block copolymer composed of α-methylstyrene polymerblocks and conjugated diene polymer blocks or the unhydrogenatedtriblock or radial teleblock copolymer obtained by reacting thepolyfunctional coupling agent with a living polymer of the blockcopolymer composed of the α-methylstyrene polymer blocks and conjugateddiene polymer blocks (each of which is encompassed by the blockcopolymer (a) for use in the present invention) can be directlysubjected to hydrogenation without substituting the solvent used in theproduction process.

The hydrogenation reaction is typically carried out at a reactiontemperature of 20 to 100° C., under a hydrogen pressure of 0.1 to 10MPa, and in the presence of a hydrogenation catalyst. Examples of suchcatalysts are Raney nickel; heterogeneous catalysts composed of a metalsuch as Pt, Pd, Ru, Rh and Ni, and a carrier for carrying the metal suchas carbon, alumina and diatomite; Ziegler catalysts composed of atransition metal compound (e.g., nickel octoate, nickel naphthenate,nickel acetylacetonate, cobalt octoate, cobalt naphthenate, and cobaltacetylacetonate) in combination with an organoaluminum compound such astriethylaluminum and triisobutylaluminum, or an organolithium compound;and metallocene catalysts composed of a bis(cyclopentadienyl) compoundof transition metals such as titanium, zirconium and hafnium, incombination with an organometallic compound of lithium, sodium,potassium, aluminum, zinc, or magnesium. The unhydrogenated blockcopolymer (a) is preferably hydrogenated to a degree in which 70% ormore, more preferably 90% or more of the carbon-carbon double bonds inthe conjugated diene polymer block B. In this manner, the weatherresistance of the block copolymer (a) is increased.

The block copolymer (a) for use in the present invention is preferablyany of those obtained in the above-described process. A particularlypreferred block copolymer is obtained as follows: α-methylstyrene havinga concentration of 5 to 50% by mass is allowed to polymerize in anonpolar solvent at a temperature of −30 to 30° C. in the presence of0.1 to 10% by mass of a polar compound using an organolithium compoundas an initiator. A conjugated diene is then polymerized by adding 1 to100 molar equivalents of the conjugated diene relative to the livingpoly-α-methylstyryllithium so that it will polymerize to form a polymerblock b1 while converting the living active terminal. Subsequently, thereaction system is brought to a temperature higher than 30° C. to causeadditional conjugated diene to polymerize to form a polymer block b2.This block copolymer is preferred because of its good low temperaturecharacteristics. In this case, the polymer block B consists of polymerblocks b1 and polymer blocks b2.

While the block copolymer (a) may have straight-chained, branched, orany other proper structure, it preferably includes at least one(A-b1-b2) structure. Among such block copolymers are A-b1-b2-b2-b1-Atype copolymers, mixtures of A-b1-b2-b2-b1-A type copolymer and A-b1-b2type copolymer, and (A-b1-b2)_(n)X type copolymers (wherein X is acoupling agent residue and n is an integer of 2 or larger).

The polymer block A in the block copolymer (a) preferably has a weightaverage molecular weight in the range of 1,000 to 50,000, and morepreferably in the range of 2,000 to 40,000.

The polymer block b1 in the block copolymer (a) preferably has a weightaverage molecular weight in the range of 1,000 to 30,000, and morepreferably in the range of 2,000 to 25,000, and preferably contains lessthan 30% of 1,4-linkages originating from conjugated diene units.

The polymer block b2 in the block copolymer (a) preferably has a weightaverage molecular weight in the range of 25,000 to 190,000, and morepreferably in the range of 30,000 to 100,000, and contains 30% or more,preferably from 35% to 95%, and more preferably from 40% to 80% of1,4-linkages originating from conjugated diene units.

The block copolymer (a) in which the polymer block B is composed ofisobutylene can be obtained by a common cationic living polymerizationprocess using 1,4-di(2-methoxy-2-propyl)benzene or1,4-di(2-chloro-2-propyl)benzene. For example,poly(α-methylstyrene)-polyisobutylene-poly(α-methylstyrene) triblockcopolymer can be produced in the following manner: Isobutylene isallowed to undergo cationic polymerization by using an initiatorcomprising 1,4-di(2-methoxy-2-propyl)benzene or1,4-di(2-chloro-2-propyl)benzene combined with a Lewis acid such astitanium tetrachloride and optionally adding pyridine or2,6-di-t-butylpyridine. The reaction is carried out at a temperature of−10 to −90° C. in a hydrocarbon solvent such as hexane andmethylcyclohexane, or a halogenated hydrocarbon solvent such as methylchloride and methylene chloride. This gives a living polymer.Subsequently, α-methylstyrene is cationically polymerized to give thedesired poly(α-methylstyrene)-polyisobutylene-poly(α-methylstyrene)triblock copolymer.

The acrylic resin (b) for use in the polymer composition of the presentinvention is a homopolymer of methyl methacrylate or a copolymercomposed of methyl methacrylate, the major component, and othercopolymerizable monomers. Examples of such copolymerizable monomersinclude acrylic acid and metal salts thereof; acrylic acid esters suchas methyl acrylate, ethyl acrylate, n-butyl acrylate, s-butyl acrylate,t-butyl acrylate and 2-ethylhexyl acrylate; methacrylic acids and metalsalts thereof; methacrylic acid esters such as ethyl methacrylate,n-butyl methacrylate, s-butyl methacrylate, t-butyl methacrylate,2-hydroxyethyl methacrylate, glycidyl methacrylate and cyclohexylmethacrylate; vinyl acetate; aromatic vinyl compounds such as styrene,α-methylstyrene and p-methylstyrene; maleic anhydride; and maleimidecompounds such as N-methylmaleimide, N-phenylmaleimide andN-cyclohexylmaleimide.

To copolymerize these monomers with methyl methacrylate, the monomersmay be used either individually or in combination of two or moremonomers. It is preferred that the copolymer composed of methylmethacrylate and other copolymerizable monomers contain thecopolymerizable monomers in a proportion that does not significantlyaffect the properties of the acrylic resin. The proportion of thecopolymerizable monomers is preferably 30% by mass or less, and morepreferably 25% by mass or less.

The acrylic resin (b) can be produced by a common polymerizationtechnique, such as solution polymerization, emulsion polymerization andsuspension polymerization, and can be produced by any proper method. Anyproper known acrylic resin can serve as the acrylic resin (b) for use inthe present invention. Examples include ACRYPET (product name)manufactured by Mitsubishi Rayon Co., Ltd., DELPET (product name)manufactured by Asahi Kasei Corporation, SUMIPEX (product name)manufactured by Sumitomo Chemical Co., Ltd., and PARAPET (product name)manufactured by Kuraray Co., Ltd.

The softener (c), which is optionally used in the polymer composition ofthe present invention, may be any of known softeners, includinghydrocarbon-based oils such as paraffin-, naphthene- and aromatic-basedoils; vegetable oils such as peanut oil and rosin; phosphoric acidesters; low-molecular-weight polyethylene glycol; liquid paraffin; andhydrocarbon-based synthetic oils such as low-molecular-weightpolyethylene, oligomers of ethylene-α-olefin copolymer, liquidpolybutene, liquid polyisoprene or hydrogenated products thereof, andliquid polybutadiene or hydrogenated products thereof. These softenersmay be used either individually or in combination of two or more. Of thedifferent softeners, paraffin-based hydrocarbon oils andhydrocarbon-based synthetic oils, including oligomers ofethylene-α-olefin copolymer, are preferably used as the softener (c) foruse in the present invention.

The blowing agent (d), which is added to the polymer composition of thepresent invention to prepare foam compositions, includes, for example,inorganic blowing agents such as sodium bicarbonate and ammoniumbicarbonate; and organic blowing agents, including azo compounds such asazodicarbonamide, barium azodicarboxylate and azobisisobutyronitrile,nitroso compounds such as N,N′-dinitrosopentamethylenetetramine andN,N′-dinitroso-N,N′-terephthalamide, and hydrazide compounds such asp-toluenesulfonylhydrazide. These blowing agents may be used eitherindividually or in combination of two or more. Of the different blowingagents, azodicarbonamide, N,N′-dinitrosopentamethylenetetramine andhydrazide compounds are particularly preferred.

To ensure smooth foaming of the blowing agent (d), a known foaming aid,including metal salts of aliphatic monocarboxylic acids, metal salts ofalkylarylsulfonic acids, urea and urea derivatives, may optionally beadded. Examples of the metal salts of aliphatic monocarboxylic acidsinclude alkali metal (e.g., Li, Na and K) salts or alkaline earth metal(e.g., Mg and Ca) salts of caprylic acid, capric acid, lauric acid,myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid,hydroxystearic acid, erucic acid, behenic acid and montanic acid.Examples of the metal salts of alkylarylsulfonic acids include alkalimetal salts or alkaline earth metal salts of alkylbenzenesulfonic acidssuch as p-toluenesulfonic acid and dodecylbenzenesulfonic acid, and ofalkylnaphthalenesulfonic acids such as isopropylnaphthalenesulfonicacid, dibutylnaphthalenesulfonic acid and amylnaphthalenesulfonic acid.

The polymer composition of the present invention needs to contain theblock copolymer (a), the acrylic resin (b), and the softener (c) inrespective proportions (by mass) such that each of the followingrelationships (1) and (2) holds:0.05≦Wb/Wa≦2  (1) andWc/(Wa+Wb+Wc)≦0.5  (2)wherein Wa, Wb, and Wc represent the amounts (by mass) of the blockcopolymer (a), the acrylic resin (b), and the softener (c),respectively.

Also, the foam composition obtained by adding the blowing agent (d) tothe polymer composition of the present invention needs to contain theblowing agent (d) in a proportion (by mass) such that the followingrelationship (3) holds:0.01≦Wd/(Wa+Wb+Wc)≦0.1  (3).

If the value of Wb/Wa, or the ratio (by mass) of the amount of theacrylic resin (b) to the amount of the block copolymer (a) in thepolymer composition, is smaller than 0.05, then the formability of thepolymer composition and the foam composition is decreased, as are thescratch resistance of molded articles and layers formed of the polymercomposition and of foams obtained by foaming the foam composition andthe extension stress of stretch materials formed of the polymercomposition. In comparison, if the ratio is larger than 2, then theflexibility, the rubber elasticity, the mechanical strength, the stressrelaxation property, and the tensile permanent set of the polymercomposition, molded articles thereof, stretchable materials and layersformed of the polymer composition, and the foam composition and foamsobtained by foaming the foam composition become insufficient. Morepreferably, the value of Wb/Wa lies in the range of 0.1 to 1.6.

Also, if the value of Wc/(Wa+Wb+Wc), or the ratio (by mass) of theamount of the softener (c) to the total amount of the block copolymer(a), the acrylic resin (b), and the softener (c), is larger than 0.5,then the scratch resistance, the abrasion resistance, the mechanicalstrength, and the expansion ratio of the polymer composition, moldedarticles and layers formed of the polymer composition, and the foamcomposition and foams obtained by foaming the foam composition becomeinsufficient. Also, a decrease will result in the mechanical strength,the extension stress, the stress relaxation property, and the tensilepermanent set of stretchable materials formed of the polymercomposition.

Moreover, if the value of Wd/(Wa+Wb+Wc), or the ratio (by mass) of theblowing agent (d) to the total amount of the block copolymer (a), theacrylic resin (b), and the softener (c), falls in the range of0.01≦Wd/(Wa+Wb+Wc)≦0.1, then the foam composition and the foams obtainedby foaming the foam composition have an expansion ratio, scratchresistance, abrasion resistance, rubber elasticity, and mechanicalstrength in a well-balanced manner. If the ratio (by mass) of theblowing agent (d) is larger than 0.1, then bubbles in the foam obtainedby foaming the form composition may not be formed as independent bubblesand are connected to one another to form larger bubbles. This results ina decrease in physical properties such as scratch resistance, abrasionresistance, rubber elasticity, and mechanical strength. To obtain a foamthat is composed mostly of independent bubbles and thus exhibitsfavorable physical properties, it is preferred to select a suitableblowing agent (d) depending on the physical properties, such as meltviscosity, and the proportion of each component of the foam composition.

The polymer composition of the present invention, which contains theblock copolymer (a), the acrylic resin (b), and the softener (c) inamounts that satisfy the above-described relationships (1) and (2), ischaracteristic in that it has a morphology in which the block copolymer(a) forms a continuous phase (i.e., matrix), throughout which theacrylic resin (b) is dispersed to form sea-island structures (This isalso the case with the foam composition). Such a polymer composition (orfoam composition) can exhibit flexibility, high rubber elasticity, goodstress relaxation property, and heat resistance (e.g., compressionpermanent set at 70° C.) because of the block copolymer (a) formingmatrix, which also contributes to the reduction of the tensile permanentset. Furthermore, the presence of acrylic resin (b), which provides ahigh transparency, scratch resistance and abrasion resistance, in theblock copolymer (a) matrix in the form of a dispersed particle phasesignificantly improves, while retaining the flexibility and high rubberelasticity of the block copolymer (a), the formability, transparency,extension stress, scratch resistance, and abrasion resistance of thepolymer composition as compared to the block copolymer (a) alone.

The polymer composition is particularly preferred when the acrylic resin(b) is dispersed in such a manner that the dispersed particles have anaverage dispersed particle size of 0.2 μm or less since the improvementin the above-described physical properties is more significant.

One preferred method to disperse the acrylic resin (b) in the polymercomposition (or the foam composition) of the present invention so thatthe dispersed particles have an average dispersed particle size of 0.2μm or less is to suitably select each component so that the acrylicresin (b), and the block copolymer (a) or a mixture of the blockcopolymer (a) and the softener (c), have melt viscosities that are asclose to each other as possible at the kneading temperature and theshear rate upon kneading, although the acrylic resin (b) may bedispersed by other methods depending on the ratio (Wb/Wa) of the acrylicresin (b) to the block copolymer (a) and the amount of the softener (c).

The dispersed particle phase of the acrylic resin (b) and the matrix ofthe block copolymer (a) present in the polymer composition (or the foamcomposition) of the present invention can be observed using, forexample, a transmission electron microscope.

Specifically, a 2 mm thick sheet-like article is injection-molded fromthe polymer composition (or the foam composition) and is sliced with amicrotome under freezing conditions. The slices are stained withruthenate and the cross-sections are observed with a transmissionelectron microscope. In this manner, the block copolymer (a) and theacrylic resin (b) are observed forming the matrix and the dispersedparticle phase, respectively. The average dispersion particle size ofthe acrylic resin (b) can be determined by measuring the length of themajor axis of the observable dispersed particles by themicrophotography, dividing the length by the magnification of themicrophotography, and then taking the average over 100 measurements.

When necessary, the polymer composition of the present invention mayfurther contain a thermoplastic polymer different from theabove-described block copolymer (a) and the acrylic resin (b), a rubberreinforcing agent, or a filler, provided that these agent do not affectthe advantages of the present invention.

Examples of the different thermoplastic polymers include olefin-basedresins such as various polyethylenes, polypropylenes,ethylene-polypropylene random copolymers, and ethylene-vinylacetatecopolymers; styrene-based resins such as polystyrene,poly(α-methylstyrene), and styrene-acrylonitrile copolymers;styrene-based block copolymers containing styrene blocks as the hardsegments which are different from the block copolymer (a); polyphenyleneoxides; polycarbonates; and olefin-based thermoplastic elastomers. Thesemay be used either individually or in combination of two or more. Whenused, the different thermoplastic polymer is preferably added in amountsnot exceeding 10% by mass relative the polymer composition.

The rubber reinforcing agents and the fillers include inorganic fillerssuch as carbon black, calcium carbonate, talc, silica and diatomite; andorganic fillers such as rubber powder and wood filler. These may be usedindividually or in combination of two or more. When used, the rubberreinforcing agent or the filler is added preferably in amounts notexceeding 30% by mass relative to the polymer composition.

As long as the advantages of the present invention are not affected, thepolymer composition of the present invention may further contain athermal stabilizer, an antioxidant, a light stabilizer, a flameretardant, an antistatic agent, a pigment, and a crosslinking agent.

The mixing technique to obtain the polymer composition or the foamcomposition of the present invention may be any conventional technique.For example, the components can be mixed by using a kneader such as asingle screw extruder, a twin screw extruder, a Banbury mixer, abrabender, an open roll, or a kneader to obtain the polymer compositionof the present invention. This kneading process is typically carried outat a temperature in the range of 160 to 280° C., preferably in the rangeof 190 to 260° C. To obtain the foam composition, the kneading ispreferably carried out at a temperature in the range of 170 to 260° C.in view of the decomposition temperature of the blowing agent.

The kneading may be achieved by using any of the following techniques:(1) all of the components of the polymer composition or the foamcomposition are first dry-blended together using a Henschel mixer or atumbler mixer and are subsequently kneaded at once; (2) all thecomponents except the softener (c) are first kneaded together and apredetermined amount of the softener (c) is subsequently fed to thekneader through a side feeder; and (3) all the components except theacrylic resin (b) are first kneaded together and a predetermined amountof the acrylic resin (b) is fed to the kneader through a side feeder.

In cases where the decomposition temperature of the blowing agent (d) islower than the heating temperature required during the kneading processto obtain the foam composition, all the components except the blowingagent (d) are first kneaded by using one of the above-describedtechniques and temporarily formed into pellets, into which the blowingagent (d) is dry-blended and the mixture is then fed to a moldingapparatus. Alternatively, the pellets formed by kneading all thecomponents except the blowing agent (d) may be fed to a moldingapparatus and the blowing agent (d) is subsequently introduced into themolding apparatus via a post-introduction means, such as a side feeder,as the pellets are molded. In the latter case, a master batch may firstbe made by kneading a high concentration of the blowing agent (d) withthe other thermoplastic resin at a temperature lower than thedecomposition temperature of the blowing agent (d) and this master batchmay be introduced into the molding apparatus.

In cases where the decomposition temperature of the blowing agent (d) ishigher than the heating temperature required during the kneading processto obtain the foam composition, the blowing agent (d) may be introducedeither along with the other components or during the kneading process.When all the components except the blowing agent (d) are first kneadedtogether and temporarily formed into pellets to be fed to a moldingapparatus, the blowing agent (d) may be first dry-blended with thepellets and the mixture is then fed to the molding apparatus.Alternatively, the pellets formed by kneading all the components exceptthe blowing agent (d) may be fed to a molding apparatus and the blowingagent (d) is subsequently introduced into the molding apparatus via apost-introduction means, such as a side feeder, as the pellets aremolded. In the latter case, a master batch may first be made by kneadinga high concentration of the blowing agent (d) with the otherthermoplastic resin at a temperature lower than the decompositiontemperature of the blowing agent (d) and this master batch may beintroduced into the molding apparatus.

The polymer composition of the present invention may be formed intosheets, films, tubes, hollow articles, articles molded in a mold, andvarious other molded articles, using a known molding technique such asextrusion molding, injection molding, blow molding, compression molding,press molding, and calendering. In addition, the polymer composition ofthe present invention can be used to form composite articles with othermaterials (including polymer materials such as polyethylene,polypropylene, olefin-based thermoplastic elastomers,acrylonitrile-butadiene-styrene resins (ABS resins), and polyamides; andvarious types of metal, wood, and cloth) by using the two-color moldingtechnique.

Similarly, the foam composition of the present invention can also beformed into various foamed articles such as sheets, films, tubes, hollowarticles, and articles molded in a mold, using a known shaping techniquesuch as extrusion molding, injection molding, blow molding, compressionmolding, press molding, and calendering. The composition may be foamedeither during or after the forming process. To ensure that the resultingfoams have desired physical properties, the foam composition ispreferably filled into, if required, a mold to a certain filling ratioor higher and then foamed so that the bubbles in the foam can remainindependent and do not form larger bubbles. Again, the foam compositionof the present invention can be used to form composite articles withother materials (including polymer materials such as polyethylene,polypropylene, olefin-based thermoplastic elastomers, ABS resins, andpolyamides; and various types of metal, wood, and cloth) by using thetwo-color molding technique.

That the articles formed of the polymer composition of the presentinvention have a particularly high abrasion resistance is demonstratedby the fact that a 2 mm thick sheet-like article made of the polymercomposition gives a Taber abrasion of 50 mm³ or less, preferably 30 mm³or less, when tested according to JIS K 6264 using an H-22 abrasionwheel under conditions of 1 kg load and 1000 rpm (See, Examples below).The polymer composition of the present invention, which gives a Taberabrasion falling within the above-specified range when tested under theabove-described conditions, has proven to be advantageous in that it hashigh durability in use and in that it is cost-effective as it canminimize the amount of the material used.

The polymer composition described above can be used to fabricatestretchable materials of the present invention, including films, bands,strands, nonwoven fabrics, and any other stretchable form suitable for adesired application.

According to the present invention, the stretchable materials can befabricated from the polymer composition by using any of the commonlyused forming processes that is suited to the form of a desiredstretchable material. In case of fabricating films, strands, and bands,for example, films and bands can be made by using a T-die, and strandscan be made by using a strand die, on a single or twin screw extruder.When it is desired to fabricate nonwoven fabrics, the polymercomposition can be melt-spun, for example, on a common melt-blownnonwoven fabric-making apparatus and the spun fibers are formed into afiber web on a collection surface to make a melt-blown nonwoven fabric.Alternatively, nonwoven fabrics can be fabricated by a spun-bond processin which a fiber web is first formed and heat is then applied by a rollto partially adhere the fibers at their intersections.

The formation of the stretchable materials from the polymer compositionis preferably carried out at a temperature of 160 to 300° C., andpreferably at a temperature of 170 to 290° C.

When the stretchable material is a film, it is preferably 15 μm to 200μm thick while it may have any thickness or width. When the stretchablematerial is a strand, it preferably has a circular, elliptical, orrectangular cross-section while it may have any cross-sectional shape.When the stretchable material is a band, it is preferably 200 μm to 2 mmthick while it may have any thickness or width.

When the stretchable material is a nonwoven fabric, the fibers formingthe nonwoven fabric may have any degree of fineness or Metsuke that issuitable for a desired application. The fibers forming such stretchablenonwoven fabrics preferably are long fibers with uniform degree offineness in terms of the extension stress, the stress relaxationproperty, and the residual strain. Such nonwoven fabrics preferably havea Metsuke in the range of 5 to 200 g/m² in terms of ease of handle.

Not only do the stretchable materials formed of the polymer compositionof the present invention exhibit various favorable properties, includingthe formability, mechanical strength, flexibility, and rubberelasticity, that are attributable to the polymer composition, but alsoshow a good stress relaxation property, extension stress, and tensilepermanent set. Of the different stretchable materials that can beproduced according to the present invention, preferred are those thatyield a 0.8 MPa or larger stress when formed into a 1 mm thick, No. 2dumbbell-molded sample piece according to JIS K 6251 and stretched by50% at a test speed of 20 mm/min at 25° C. with the grip distance of 70mm and that, at the same time, can give a 50% or a higher stressretention after held under the described conditions for 2 hours. Thisstretchable material enables formation of thin film and a reduction inMetsuke, leading to a cost reduction and a saving of resources. Morepreferably, the stretchable material is such that it gives an extensionstress of 1 MPa or larger when measured under the above-describedconditions (measured when stretched by 50%). While no specific limitsexist regarding the upper limits of the extension stress, thestretchable material preferably gives an extension stress of 15 MPa orless, and preferably 10 MPa or less in order to be of practical use.More preferably, the stretchable material is such that it has a stressretention of 70% or more under the above-described conditions.

A description will now be given of a laminate produced according to thepresent invention that includes a layer formed of the above-describedpolymer composition and other layers formed of other materials.

The other materials for forming the other layers in the laminate of thepresent invention include thermoplastic resins, and various types ofmetal, cloth, leather, glass, and wood. Of these, thermoplastic resinsare preferred. Examples of such thermoplastic resins includepolyphenylene ether-based resins; polyamide-based resins such aspolyamide 6, polyamide 6.6, polyamide 6.10, polyamide 11, polyamide 12,polyamide 6.12, polyhexamethylenediamine terephthalamide, andpolyhexamethylenediamine isophthalamide; polyester-based resins such aspolyethylene terephthalate and polybutylene terephthalate; acrylicresins such as poly(methyl acrylate) and poly(methyl methacrylate);polyoxymethylene-based resins such as polyoxymethylene homopolymer andpolyoxymethylene copolymer; styrene-based resins such as polystyrene,acrylonitrile-styrene resin (AS resin), andacrylonitrile-butadiene-styrene resin (ABS resin); polycarbonate resins;ethylene-propylene rubber (EPM) and ethylene-propylene-nonconjugateddiene rubber (EPDM); styrene-based thermoplastic elastomers such asstyrene-butadiene block copolymers, styrene-isoprene block copolymers,and hydrogenated products thereof; olefin-based thermoplasticelastomers; chlorosulfonated polyethylene; polyurethane-basedthermoplastic elastomers; polyamide-based thermoplastic elastomers;polyester-based thermoplastic elastomers; and resin compositionscontaining styrene-based thermoplastic elastomers, for example, resincompositions containing a styrene-based thermoplastic elastomer, anolefin-based resin, and a softener. Of these, preferred are olefin-basedresins, olefin-based thermoplastic elastomers, and styrene-basedthermoplastic elastomers or resin compositions containing styrene-basedthermoplastic elastomers.

Any proper forming technique can be employed to make the laminate of thepresent invention, including injection molding such as insert injectionmolding, two-color injection molding, core back type injection molding,sandwich injection molding and injection press molding; extrusionmolding such as T-die lamination, coextrusion, and extrusion coating;blow molding; calendering; press molding; slush molding; and moldingtechniques that involves a melt, such as melt casting. The laminate canbe formed into sheets, films, tubes, molded articles, and various otherforms.

Of the different molding techniques shown above, the insert injectionmolding is generally performed by forming a different material into apredetermined size and shape in advance, inserting the material in amold, and injecting the polymer composition in the mold to form alaminate. The different material for insertion into the mold may beshaped by any suitable method. When the different material to form theinsert is a thermoplastic resin or a rubber, it may be molded by anysuitable technique, including injection molding, extrusion molding,calendering followed by cutting into a predetermined size, pressmolding, and casting. When the different material to form the insert isa metal material, it may be formed into a predetermined size and shapein advance by any of the techniques commonly used in the production ofmetallic products (e.g., casting, rolling, cutting, machining, andgrinding).

When the two-color injection molding is employed to make a laminate, twoor more injection molding machines are used: First, one is used toinject a different material (e.g., thermoplastic resin) into a firstmold cavity to form a first article, which is then replaced by a secondmold through rotation or transfer of the molds, and then the othermolding machine is used to inject the polymer composition into the gapformed between the first article and the inner walls of the second mold,forming a desired laminate. When the core back type injection molding isemployed to make a laminate, a single injection molding machine is usedin conjunction with a single mold: First, a different material isinjected into a mold to form an article. The cavity of the mold is thenexpanded to a larger cavity and the polymer composition is injected intothe enlarged cavity to form a desired laminate.

In the injection molding method described above, the order of injectingthe materials may be reversed: The polymer composition may be firstinjected into a mold to form a first article, which is followed byinjection of the different material (e.g., thermoplastic resin) to formthe laminate.

When the extrusion molding is employed to make a laminate including alayer of the polymer composition and a layer of a different material, amold (i.e., an extrusion die) having two or more compartments arrangedrelative to one anther, for example, one outside the other, one on topof the other, or side by side, is used, and the polymer composition andthe different material (e.g., thermoplastic resin) are simultaneouslyextruded through the respective compartments. The separately extrudedmaterials are then fused with each other to form a desired laminate.When the different material is not thermoplastic, the melted polymercomposition can be extruded over, or around, the different material tocoat the different material and to thereby form a desired laminate. Whenthe calendering is employed, the melted polymer composition is coated orlaminated onto the different material, which is provided in a molten,plasticized state or in a solid state, via a calendering process to givea desired laminate. When the press molding is employed, the differentmaterial is predisposed and the polymer composition is melt press moldedthereonto to form a laminate.

Alternatively, the polymer composition, the different material, and,when necessary, additional materials may be used to form individuallayers, which in turn are overlaid on top of one another and are pressedwhile heated to fuse the layers and to thus form a laminate. Theindividual layers may be adhered together by an adhesive, a tackinessagent, or a primer.

By using the polymer composition layer to serve as the outermost layerin the laminate of the present invention, the laminate can takeadvantage of the favorable properties of the polymer composition,including scratch resistance, abrasion resistance, and flexibility.

Aside from such properties as formability, flexibility, mechanicalstrength, rubber elasticity, and transparency, the polymer compositionof the present invention exhibits high scratch resistance and highabrasion resistance. These properties can be exploited in moldedarticles of the polymer composition, foams formed of the polymercomposition with a blowing agent, or laminates described above suitablefor use in a wide range of applications, including exterior and interiorparts of automobiles such as bumpers, body side moldings, weatherstrips,mat guards, emblems, leather sheets, floor mattress, arm rests, air bagcovers, steering wheel covers, belt line moldings, flush mounts,instrument panels, center console boxes, door trims, pillars, assistgrips, and sheet covers; functional parts of automobiles, including rackand pinion gear boxes, suspension covers, and constant velocity jointboot; parts for home electronic appliances such as gaskets forrefrigerators, hoses for washing machines, bumpers for vacuum cleaners,protective film for cellular phones, and waterproof bodies; parts foroffice machines such as feeder rollers, winding rollers, and cleanernozzles for photocopiers; furniture such as seat upholsteries for sofasand chairs; parts for switch covers, casters, stoppers, and leg rubbertips; coating materials such as wire coatings, and coatings for steelplates and plywood; medical instruments such as syringe gaskets, androlling tubes; industrial materials such as industrial parts withpackings and seals, hoses, tubes, conveyor belts, electric belts, andpelletizer rolls; wrapping materials such as construction materialsincluding sealing packings for doors and windowsills, wrappings fordaily commodities, and wrappings for industrial materials; protectivefilm and protective sheets for floorings, furniture, and buildingmaterials; grip materials for various equipment (such as scissors,screwdrivers, toothbrush, ski poles, and pens); footwears (such asmen's, ladies', and school children's shoes, sports shoes, safety shoes,ski shoes, and sandals); sports equipment such as water goggles,snorkels, wet suits, and protectors; leisure goods; stationeries; toys;and information equipment.

Taking advantage of the above-described advantageous properties, thestretchable materials formed of the polymer composition of the presentinvention can be effectively used, either alone or by overlaying with apiece of stretchable cloth such as stretchable cloth and pleated cloththat are stretchable at least in one direction, in a wide rage ofapplications, including sanitary products such as disposable diapers,toilet training pants, sanitary napkins, and undergarments; medicalmaterials such as bases for fomentation, stretchable tapes, bandages,operating gowns, supporters, and orthodontic wears; band applicationssuch as hair bands, wrist bands, wrist watch bands, and eye glassesbands; and miscellaneous items such as rubber bands, and training tubes.Similarly, the foams of the present invention can be used in thedescribed applications as a stretchable material.

The present invention will now be described in further detail withreference to Examples, which are not intended to limit the scope of theinvention in any way.

[I] Evaluation of Physical Properties of Articles Formed of the PolymerComposition

In the following Examples and Comparative Examples, articles formed ofrespective polymer compositions were tested or evaluated for each of thescratch resistance, the abrasion resistance, the transparency, therubber elasticity, the flexibility, the mechanical strength, the averagedispersed particle size of the acrylic resin (b) in respectivemorphologies, and the formability of the polymer composition. The testsand evaluations were performed according to the following methods:

a) Scratch Resistance

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 5 cm (width)×11 cm(length)×0.2 cm (thickness) sample piece by press molding (moldingtemperature=230° C., press pressure=10 MPa, press time=3 min). Accordingto ASTM D2197, each sample piece was scratched with a needle-like jigdesigned for the crosscut test at a speed of 1 cm/sec while applying aload of 200 g. The depth of the resulting scratches was measured by asurface roughness meter. A sample with shallower scratches wasconsidered to have a higher scratch resistance.

b) Abrasion Resistance

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 11 cm (width)×11 cm(length)×0.2 cm (thickness) sample piece by press molding (moldingtemperature=230° C., press pressure=10 MPa, press time=3 min). Accordingto JIS K 6264, each sample piece was measured for the Taber abrasionusing an H-22 abrasion wheel under conditions of 1 kg load and 1000 rpm.A sample with less abrasion was considered to have a higher abrasionresistance.

c) Transparency

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 11 cm (width)×11 cm(length)×0.2 cm (thickness) sample piece by press molding (moldingtemperature=230° C., press pressure=10 MPa, press time=3 min). Totaltransmittance of each sample piece was determined from the absorptionspectrum for visible light for that sample. A sample with a higher totaltransmittance was considered to have a higher transparency.

d) Rubber elasticity

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 2 mm thick sheet bypress molding (molding temperature=230° C., press pressure=10 MPa, presstime=3 min). A No. 1 dumbbell-molded sample piece was stamped out fromeach sheet. According to JIS K 6262, each sample piece was stretched by100%, was held stretched for 24 hours, and was then released. Thetensile permanent set (%) was measured as an index of the rubberelasticity. A sample with a smaller tensile permanent set was consideredto have a higher rubber elasticity.

e) Flexibility (Hardness)

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 11 cm (width)×11 cm(length)×0.2 cm (thickness) sample piece by press molding (moldingtemperature=230° C., press pressure=10 MPa, press time=3 min). Accordingto JIS K 6253, the hardness of each sample was measured using the type Adurometer as an index of the flexibility.

f) Mechanical Strength

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 2 mm thick sheet bypress molding (molding temperature=230° C., press pressure=10 MPa, presstime=3 min). A No. 5 dumbbell-molded sample piece was stamped out fromeach sheet. According to JIS K 6251, a tensile test was conducted andthe breaking strength and the breaking stretch were measured as an indexof the mechanical strength.

g) Average Dispersed Particle Size

Each of the polymer compositions obtained in Examples 1 through 13 andComparative Examples 1 through 7 was used to make a 2 mm thick sheet bypress molding (molding temperature=230° C., press pressure=10 MPa, presstime=3 min). Using a microtome, each sheet was sliced under freezingconditions. The slices were stained with ruthenate and thecross-sections were observed with a transmission electron microscope.The average dispersion particle size of the acrylic resin (b) that formsa dispersed particle phase was determined by measuring the length of themajor axis of the observable dispersed particles, dividing the length bythe magnification of the microphotography, and then taking the averageover 100 measurements.

h) Formability

According to JIS K 7210, each of the pellet-like polymer compositionsobtained in Examples 1 through 13 and Comparative Examples 1 through 7was measured for the melt flow rate (MFR) at 230° C. under a load of2.16 kg. A sample with a higher MFR value was considered to have ahigher formability.

The components used in the following Examples and Comparative Exampleswere prepared as follows:

(a) Block Copolymers

POLYMERIZATION EXAMPLE 1

-   (1) 172 g of α-methylstyrene, 251 g of cyclohexane, 47.3 g of    methylcyclohexane, and 5.9 g of tetrahydrofuran were placed in a    pressure container equipped with a stirrer and having the atmosphere    inside replaced with nitrogen. To this mixture, 16.8 ml of    sec-butyllithium (1.3M cyclohexane solution) was added and the    polymerization was allowed to proceed at −10° C. for 5 hours. Three    hours after initiation of the polymerization, the weight average    molecular weight of the poly(α-methylstyrene) (block A) was    determined by GPC relative to polystyrene standards and was    determined to be 6600, indicating a 90% conversion rate of the    α-methylstyrene into the polymer. To the resulting reaction mixture,    35.4 g of butadiene was added and the mixture was stirred at −10° C.    for 30 minutes to carry out the polymerization of blocks b1. Then,    1680 g of cyclohexane was added. At this point, the conversion rate    of the α-methylstyrene into the polymer was 90% and the weight    average molecular weight of the polybutadiene blocks (b1) was 3700    (as measured by GPC relative to polystyrene standards). The amount    of 1,4-linkages as determined by ¹H-NMR was 19%.

Subsequently, 310 g of butadiene was further added to the reactionmixture and the polymerization was allowed to proceed at 50° C. for 2hours. At this point, samples of the block copolymer (structure:A-b1-b2) were taken and the weight average molecular weight of thepolybutadiene block (b2) was determined to be 29800 (as measured by GPCrelative to polystyrene standards). The amount of 1,4-linkages asdetermined by ¹H-NMR was 60%.

-   (2) Subsequently, 21.8 ml of dichlorodimethylsilane (0.5M toluene    solution) was added to the polymerization mixture and the mixture    was stirred at 50° C. for 1 hour to obtain a    poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene) triblock    copolymer. At this point, the coupling efficiency was determined    from the ratio in area of the UV absorbance (at 254 nm) of the GPC    of the coupled form (i.e.,    poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene) triblock    copolymer: A-b1-b2-X-b2-b1-A) to that of the unreacted block    copolymer (i.e., poly(α-methylstyrene)-polybutadiene block    copolymer: A-b1-b2) and was determined to be 94%. The results of    ¹H-NMR analysis revealed that the amount of the α-methylstyrene    polymer block relative to the    poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene) triblock    copolymer was 31% and the amount of 1,4-linkages in total butadiene    polymer block B (i.e., block b1 and block b2) was 55%.-   (3) To the polymerization mixture obtained in (2) above, a Ziegler    hydrogenation catalyst composed of nickel octoate and    triethylaluminum was added under hydrogen atmosphere. The    hydrogenation was then allowed to take place at 80° C. for 5 hours    under hydrogen pressure of 0.8 MPa to give hydrogenated products of    the poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene)    triblock copolymer (which is referred to as “block copolymer 1,”    hereinafter). The results of GPC analysis performed on the resulting    block copolymer 1 revealed that the major component of the block    copolymer 1 is a hydrogenated product (i.e., coupled form) of a    poly(α-methylstyrene)-polybutadiene-poly(α-methylstyrene) triblock    copolymer with Mt (peak top of average molecular weight)=81000, Mn    (number average molecular weight)=78700, Mw (weight average    molecular weight)=79500, and Mw/Mn (distribution of molecular    weights)=1.01. The amount of the coupling form as determined from    the ratio in area of the UV absorbances (at 254 nm) of GPC results    was 94%. The results of ¹H-NMR analysis indicated that the degree of    hydrogenation of the butadiene block B composed of the block b1 and    the block b2 was 97.5%. These results are summarized in Table 1.

POLYMERIZATION EXAMPLE 2

The reaction was carried out in the same manner as in PolymerizationExample 1, except that the amount of sec-butyllithium (1.3M cyclohexanesolution) used was 9.0 ml, rather than 16.8 ml, and the amount ofdichlorodimethylsilane (0.5M toluene solution) used was 11.6 ml, ratherthan 21.8 ml, to obtain a block copolymer (which is referred to as“block copolymer 2,” hereinafter). The molecular characteristics of theblock copolymer 2 were determined as in Polymerization Example 1. Theresults are summarized in Table 1.

POLYMERIZATION EXAMPLE 3

The reaction was carried out in the same manner as in PolymerizationExample 1, except that the amount of sec-butyllithium (1.3M cyclohexanesolution) used was 4.5 ml, rather than 16.8 ml, and the amount ofdichlorodimethylsilane (0.5M toluene solution) used was 5.8 ml, ratherthan 21.8 ml, to obtain a block copolymer (which is referred to as“block copolymer 3,” hereinafter). The molecular characteristics of theblock copolymer 3 were determined as in Polymerization Example 1. Theresults are summarized in Table 1.

POLYMERIZATION EXAMPLE 4

800 g of methylene chloride, 1200 g of methylcyclohexane, 0.97 g of1,4-bis(2-chloro-2-propyl)benzene, 1.74 g of 2,6-di-t-buthylpyridine,0.66 g of pyridine, and 210 g of isobutylene were placed in a pressurecontainer equipped with a stirrer and having the atmosphere insidereplaced with nitrogen. The mixture was cooled to −78° C. Following theaddition of 12.3 g of titanium tetrachloride, the mixture was stirredfor 4 hours. Subsequently, 1.74 g of 2,6-di-t-butylpyridine and 90 g ofα-methylstyrene were added to the reaction mixture and thepolymerization was allowed to proceed at −78° C. for additional 4 hoursto give a poly(α-methylstyrene)-polyisobutylene-poly(α-methylstyrene)triblock copolymer (which is referred to as “block copolymer 4,”hereinafter). The molecular characteristics of the block copolymer 4were determined as in Polymerization Example 1. The results aresummarized in Table 1.

POLYMERIZATION EXAMPLE 5

172 g of styrene and 2000 g of cyclohexane were placed in a pressurecontainer equipped with a stirrer and having the atmosphere insidereplaced with nitrogen. To this solution, 16.8 ml of sec-butyllithium(1.3M cyclohexane solution) was added and the polymerization was allowedto proceed at 50° C. for 1 hour. Subsequently, 345 g of butadiene wasadded to the reaction mixture and the polymerization was allowed toproceed at 50° C. for 1 hour. To the resulting reaction mixture, 21.8 mlof dichlorodimethylsilane (0.5M toluene solution) was added and themixture was stirred at 60° C. for 1 hour to obtain a reaction mixturecontaining a polystyrene-polybutadiene-polystyrene triblcok copolymer.To this reaction mixture, a Ziegler hydrogenation catalyst composed ofnickel octoate and triethylaluminum was added and the hydrogenation wasthen allowed to take place at 80° C. for 5 hours under hydrogen pressureof 0.8 MPa to give a hydrogenated product of thepolystyrene-polybutadiene-polystyrene triblock copolymer (which isreferred to as “block copolymer 5,” hereinafter). The molecularcharacteristics of the block copolymer 5 were determined as inPolymerization Example 1. The results are summarized in Table 1.

POLYMERIZATION EXAMPLE 6

The reaction was carried out in the same manner as in PolymerizationExample 1, except that the amount of sec-butyllithium (1.3M cyclohexanesolution) used was 45.3 ml, rather than 16.8 ml, and the amount ofdichlorodimethylsilane (0.5M toluene solution) used was 58.7 ml, ratherthan 21.8 ml, to obtain a block copolymer (which is referred to as“block copolymer 6,” hereinafter). The molecular characteristics of theblock copolymer 6 were determined as in Polymerization Example 1. Theresults are summarized in Table 1.

POLYMERIZATION EXAMPLE 7

The reaction was carried out in the same manner as in PolymerizationExample 5, except that the amount of sec-butyllithium (1.3M cyclohexanesolution) used was 9.0 ml, rather than 16.8 ml, and the amount ofdichlorodimethylsilane (0.5M toluene solution) used was 11.6 ml, ratherthan 21.8 ml, to obtain a block copolymer (which is referred to as“block copolymer 7,” hereinafter). The molecular characteristics of theblock copolymer 7 were determined as in Polymerization Example 1. Theresults are summarized in Table 1.

TABLE 1 molecular characteristics of the block copolymer Polymer block BLinkage Polymer block A Rate of type of Mw Content hydrogenation Productname block (by GPC) Component (mass %) Component (%) Block copolymer 1A-B-A 79,500 α-methylstyrene 31 Butadiene 97.5 Block copolymer 2 A-B-A150,500 α-methylstyrene 31 Butadiene 97.1 Block copolymer 3 A-B-A301,000 α-methylstyrene 31 Butadiene 97.0 Block copolymer 4 A-B-A 77,000α-methylstyrene 30 Isobutylene — Block copolymer 5 A-B-A 80,500 styrene31 Butadiene 98.7 Block copolymer 6 A-B-A 29,000 α-methylstyrene 31Butadiene 97.5 Block copolymer 7 A-B-A 150,500 styrene 31 Butadiene 97.9(b) Acrylic Resins

POLYMERIZATION EXAMPLE 8

500 g of pure water was placed in a 1000 ml three-necked flask equippedwith a reflux condenser and the atmosphere inside was completelyreplaced with nitrogen. To this flask, a mixture of 425 g of methylmethacrylate, 55 g of methyl acrylate, 2.5 g of lauryl peroxide, and 4 gof lauryl mercaptan was added and the polymerization was allowed toproceed at 80° C. for 4 hours to obtain an acrylic resin (which isreferred to as “acrylic resin 1,” hereinafter). The intrinsic viscosityof the acrylic resin 1 measured at 20° C. in chloroform was 0.301 dl/g.

POLYMERIZATION EXAMPLE 9

The reaction was carried out in the same manner as in PolymerizationExample 8, except that the amount of lauryl mercaptan used was 3.5 g,rather than 4 g, to obtain an acrylic resin (which is referred to as“acrylic resin 2,” hereinafter). The intrinsic viscosity of the acrylicresin 2 measured at 20° C. in chloroform was 0.376 dl/g.

(c) Softeners

c-1: Diana Process PW-380 (product name) (a paraffin-based process oilmanufactured by Idemitsu Kosan Co., Ltd.)

EXAMPLES 1 THROUGH 13 AND COMPARATIVE EXAMPLES 1 THROUGH 7

-   (1) According to the compositions shown in Tables 2 and 3 below, one    of the block copolymers 1 through 5, the acrylic resin 1 or 2, and    the softener were mixed in respective combinations. The components    were premixed together in a Henschel mixer and the resulting mixture    was fed to a twin screw extruder (TEM-35B, manufactured by Toshiba    Machine Co., Ltd.) where it was kneaded at 230° C. and was extruded    into strands. The extruded strands were then cut to form pellets of    the polymer composition. The MFR of each polymer composition was    determined as described above and is shown in Tables 2 and 3 below.-   (2) Using an injection molding machine (IS-55EPN, manufactured by    Toshiba Machine Co., Ltd.), the pellets of each polymer composition    obtained in (1) above were formed into an article with the cylinder    temperature kept at 250° C. and the mold temperature at 80° C. In    the manner described above, the articles were tested for the scratch    resistance, abrasion resistance, transparency, rubber elasticity,    flexibility, mechanical strength, and dispersed particle size of the    acrylic resin (b). The results for each polymer composition are    shown in Tables 2 and 3 below.

TABLE 2 Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam-Exam- Exam- Exam- ple ple ple ple ple ple ple ple ple ple ple ple ple 12 3 4 5 6 7 8 9 10 11 12 13 Polymer composition (part by mass) (a) Blockcopolymer Block copolymer 1 70 54 70 54 40 36 42 65 Block copolymer 2 5249 42 35 Block copolymer 4 54 (b) Acrylic resin Acrylic resin 1 30 36 5554 43 20 20 21 28 23 36 Acrylic resin 2 30 36 (c) Softener C-1 DianaProcess 10 10 5 10 15 15 28 30 30 42 10 PW-380 Scratch resistance 1.51.9 1.5 2.3 4.5 4.6 1.8 5.4 4.1 3.9 3.6 8.1 2.0 (μm) Taber abrasion(mm³) 30 26 27 35 35 23 8 29 40 18 34 67 33 Total transmittance 89.791.4 90.3 88.6 88.6 90.7 90.5 87.1 89.8 90.4 89.8 91.4 93.0 (%) Tensilepermanent 0.8 1.0 0.5 2.0 3.0 0.5 1.2 0.5 2.8 1.8 0.8 0.0 1.2 set (%)Hardness (Type A) 80 70 81 72 90 80 70 60 50 40 33 15 70 Breakingstrength 31.2 27.9 32.0 22.7 31.5 20.9 18.0 29.9 23.3 22.2 18.8 11.221.4 (MPa) MFR (g/10 min) 1.2 10 1.0 13 5.1 12 51 42 6.5 3.9 8.9 85 18Dispersed 0.09 0.08 0.09 0.09 0.15 0.12 0.10 0.13 0.13 0.10 0.13 0.180.08 particle size (μm)

TABLE 3 Comparative Comparative Comparative Comparative ComparativeComparative Comparative Example 1 Example 2 Example 3 Example 4 Example5 Example 6 Example 7 Polymer composition (part by mass) (a) Blockcopolymer Block copolymer 1 30 24 70 Block copolymer 3 27 35 Blockcopolymer 5 70 54 (b) Acrylic resin Acrylic resin 1 70 56 18 30 36 23Acrylic resin 2 (c) Softener C-1 Diana Process PW-380 20 30 55 10 42Scratch resistance (μm) 15 19 9.8 20 10.9 12.5 11.6 Taber abrasion (mm³)230 272 321 >500 412 453 248 Total transmittance (%) 82.6 87.0 91.7 92.283.4 87.8 67.1 Tensile permanent set (%) fracture 5.0 0.0 0.0 4.7 4.05.0 Hardness (Type A) 98 82 38 8 85 70 55 Breaking strength (MPa) 5.19.8 22.4 5.0 15.2 13.1 77 MFR (g/10 min) 57 >100 61 >100 0.6 1.9 0.1Dispersed particle size (μm) N/A N/A — 0.80 0.21 0.18 N/A

REFERENCE EXAMPLE 1

Using an injection molding machine (IS-55EPN, manufactured by ToshibaMachine Co., Ltd.), a polyurethane-based thermoplastic elastomer(KURAMIRON U3190 (product name), manufactured by Kuraray Co., Ltd.)alone was formed into an article with the cylinder temperature kept at200° C. and the mold temperature at 50° C. In the manner describedabove, the article was measured or evaluated for the scratch resistanceand the abrasion resistance. The results are as shown in Table 4 below.

REFERENCE EXAMPLE 2

Using an injection molding machine (IS-55EPN, manufactured by ToshibaMachine Co., Ltd.), a polyester-based thermoplastic elastomer (HYTREL4057 (product name), manufactured by Toray-DuPont Co., Ltd.) alone wasformed into an article with the cylinder temperature kept at 210° C. andthe mold temperature at 50° C. In the manner described above, thearticle was measured or evaluated for the scratch resistance and theabrasion resistance. The results are as shown in Table 4 below.

TABLE 4 Reference Example 1 Reference Example 2 Elastomer typePolyurethane-based Polyester-based thermoplastic thermoplastic elastomer¹⁾ elastomer ²⁾ Scratch resistance 1.0 5.8 (μm) Taber abrasion 6 33(mm³) ¹⁾ KURAMIRON U3190 (product name, manufactured by Kuraray Co.,Ltd.) ²⁾ HYTREL 4057 (product name, manufactured by Toray-DuPont Co.,Ltd)

As shown in Tables 2 and 3 above, each of the polymer compositions ofExamples 1 through 13 and each of the articles formed of the respectivepolymer compositions contain one of the block copolymers (1, 2, and 4)and one of the acrylic resins (1 and 2) in proportions (by mass) thatsatisfy the relationship (1): 0.05≦Wb/Wa≦2 and contain the softener c-1in a proportion that satisfies the relationship (2): Wc/(Wa+Wb+Wc)≦0.5.As can be seen from the results of Tables 2 and 3, each of these polymercompositions and the articles formed thereof exhibits a goodformability, scratch resistance, and abrasion resistance and hastransparency, rubber elasticity, flexibility, and mechanical strength ina well-balanced manner.

Conversely, the polymer composition of Comparative Example 1, in whichthe ratio (by mass) of the acrylic resin 1 to the block copolymer 1 is2.34, a value falling outside the range given by the relationship (1),exhibits poor rubber elasticity and poor flexibility. It also shows poorscratch resistance, poor abrasion resistance, and weak mechanicalstrength.

Although the polymer composition of Comparative Example 2 contains thesoftener c-1 in a proportion that satisfies the relationship (2), theratio (by mass) of the acrylic resin 1 to the block copolymer 1 is 2.34,the same value as in Comparative Example 1 that falls outside the rangegiven by the relationship (1). This polymer composition shows poorscratch resistance, poor abrasion resistance, and weak mechanicalstrength.

The polymer composition of Comparative Example 3, which does not containthe acrylic resin 1, shows poor scratch resistance and poor abrasionresistance.

The polymer composition of Comparative Example 4, which contains thesoftener c-1 in a proportion (by mass) that does not satisfy therelationship (2) (in an excessive proportion), shows poor scratchresistance, poor abrasion resistance, and weak mechanical strength.

Each of the polymer compositions of Comparative Examples 5 and 6, inwhich the polymer block A to form the block copolymer 5 is polystyrene,exhibits poor scratch resistance, poor abrasion resistance, and weakmechanical strength, even though the ratio (by mass) of the acrylicresin 1 to the block copolymer 5 lies within the range given by therelationship (1) and the proportion (by mass) of the softener c-1satisfies the relationship (2).

The polymer composition of Comparative Example 7, in which the blockcopolymer 3 has a weight average molecular weight of more than 200,000,shows a reduced scratch resistance, abrasion resistance, and formabilityas compared to the polymer composition of Example 12 even though theratio (by mass) of the acrylic resin 1 to the block copolymer 3 fallswithin the range given by the relationship (1) and the proportion (bymass) of the softener c-1 satisfies the relationship (2).

[II] Evaluation of Physical Properties of Stretchable Materials Obtainedfrom the Polymer Composition

In the following Examples and Comparative Examples, stretchablematerials obtained from respective polymer compositions were measured orevaluated for each of the extension stress, the stress relaxationproperty, the tensile permanent set, and the formability of the polymercomposition. The measurements and evaluations were performed accordingto the following methods:

i) Extension Stress

A 1 mm thick band was obtained in each of Examples 14 through 21 andComparative Examples 8 through 12, and a No. 2 dumbbell-molded samplepiece was stamped out from each band according to JIS K 6251. The samplepiece was mounted on an Instron universal tensile tester and the stresswas measured as the sample piece was stretched by 50% at a test speed of20 mm/min at 25° C. with the grip distance of 70 mm.

j) Stress Relaxation Property

A 1 mm thick band was obtained in each of Examples 14 through 21 andComparative Examples 8 through 12, and a No. 2 dumbbell-molded samplepiece was stamped out from each band according to JIS K 6251. The samplepiece was mounted on an Instron universal tensile tester and wasstretched by 50% at a test speed of 20 mm/min at 25° C. with the gripdistance of 70 mm. The sample piece was held stretched for the following2 hours and the stress retention was measured as an index of the stressrelaxation property. A sample with a higher stress retention wasconsidered to have a higher stress relaxation property.

k) Tensile Permanent Set

A 1 mm thick band was obtained in each of Examples 14 through 21 andComparative Examples 8 through 12, and a No. 2 dumbbell-molded samplepiece was stamped out from each band according to JIS K 6251. The samplepiece was mounted on an Instron universal tensile tester and wasstretched by 100% at a test speed of 20 mm/min at 25° C. with the gripdistance of 70 mm. The sample piece was then allowed to contract at thesame speed and the percentage of the permanent set was measured when thestress measured zero.

l) Formability

In the same manner as described in section [I] h) above, pellets of thepolymer compositions obtained in Examples 14 through 21 and ComparativeExamples 8 through 12 were measured for the MFR. A sample with a higherMFR value was considered to have a higher formability.

The components used in the following Examples and Comparative Exampleswere prepared as follows:

(a) Block Copolymer

The block copolymer 1, 3, or 5 described in [I] above.

(b) Acrylic Resin

The acrylic resin 1 described in [I] above.

(c) Softener

The softener c-1 described in [I] above.

c-2: Diana Process PW-90 (product name) (a paraffin-based process oilmanufactured by Idemitsu Kosan Co., Ltd.)

EXAMPLES 14 THROUGH 21 AND COMPARATIVE EXAMPLES 8 THROUGH 12

-   (1) According to the compositions shown in Tables 5 and 6 below, the    block copolymers 1, 3, or 5, the acrylic resin 1, and the softeners    c-1 or c-2 were mixed in respective combinations. The components    were premixed together in a Henschel mixer and the resulting mixture    was fed to a twin screw extruder (TEM-35B, manufactured by Toshiba    Machine Co., Ltd.) where it was kneaded at 230° C. and was extruded    into strands. The extruded strands were then cut to form pellets of    the polymer composition. The MFR of each polymer composition was    determined as described above and is shown in Tables 5 and 6 below.-   (2) Using an extruder fitted with a T-die (LABO PLASTMILL 100C100,    manufactured by Toyo Seiki Seisaku-Sho, Ltd.), the pellets of each    polymer composition obtained in (1) above were formed into a 1 mm    thick band. The cylinder temperature was kept at 230° C. in Examples    14 and 15 and Comparative Examples 11 and 12 and at 210° C. in the    other Examples and Comparative Examples. In the manner described    above, the bands were measured for the extension stress, the stress    relaxation property, and the tensile permanent set as described    above. The measurements for each polymer composition are shown in    Tables 5 and 6 below.

TABLE 5 Example Example Example Example Example Example Example Example14 15 16 17 18 19 20 21 Polymer composition (part by mass) (a) Blockcopolymer Block copolymer 1 60 50 54 54 63 45 36 32 (b) Acrylic resinAcrylic resin 1 40 50 36 36 27 45 54 48 (c) Softener c-1 10 10 10 10 20c-2 10 Extension stress (MPa) 3.14 5.27 1.34 1.72 1.60 2.07 3.01 1.25Stress retention (%) 78 78 78 82 81 80 78 77 Tensile permanent set (%)4.97 3.99 4.50 4.29 5.00 4.08 4.63 4.77 MFR (g/10 min) 1.2 1.0 15 10 118.3 12 98

TABLE 6 Comparative Comparative Comparative Comparative ComparativeExample 8 Example 9 Example 10 Example 11 Example 12 Polymer composition(part by mass) (a) Block copolymer Block copolymer 1 30 24 27 Blockcopolymer 3 32 Block copolymer 5 54 (b) Acrylic resin Acrylic resin 1 7056 18 36 48 (c) Softener c-1 20 55 10 20 Extension stress (MPa) * 3.890.10 3.02 9.12 Stress retention (%) * 45 85 53 42 Tensile permanent set(%) * 9.00 7.40 7.93 10.0 MFR (g/10 min) 57 >100 >100 1.9 0.01 * Thesample piece was fractured during the test, so that properties could notbe determined.

As shown in Table 5 above, the stretchable materials of Examples 14through 21 are formed of the polymer compositions each containing theblock copolymer 1 and the acrylic resin 1 in proportions (by mass) thatsatisfy the relationship (1) and each containing the softener (c-1 orc-2) in a proportion that satisfies the relationship (2). As can be seenfrom the results of Table 5, each of the stretchable materials ofExamples 14 through 21 exhibits an extension stress, stress relaxationproperty, tensile permanent set, and formability in a well-balancedmanner.

In comparison, for the stretchable material of Comparative Example 8, inwhich the ratio (by mass) of the acrylic resin 1 to the block copolymer1 in the polymer composition to form the stretchable material does notfall within the range given by the relationship 1, the sample piece isfractured during the test, so that neither the stress-relieving nor thetensile permanent set could be determined.

The stretchable material of Comparative Example 9, in which the ratio(by mass) of the acrylic resin 1 to the block copolymer 1 does not fallwithin the range given by the relationship (1) despite the fact that thepolymer composition to form the stretchable material contains thesoftener c-1 at a proportion that satisfies the relationship (2), showspoor stress relaxation property, stress retention, and tensile permanentset.

The stretchable material of Comparative Example 10, in which theproportion of the softener c-1 in the polymer composition to form thestretchable material does not satisfy the relationship (2) (i.e.,excessive proportion), shows poor extension stress and tensile permanentset.

In the stretchable material of Comparative Example 11, the ratio (bymass) of the acrylic resin 1 to the block copolymer 5 in the polymercomposition to form the stretchable material falls within the rangegiven by the relationship (1) and the proportion (by mass) of thesoftener c-1 satisfies the relationship (2). In this stretchablematerial, however, the polymer block A to form the block copolymer 5 ispolystyrene, and thus the stretchable material is less favorable thanthe stretchable material of Example 17 in terms of the stress relaxationproperty, the tensile permanent set, and the formability.

In the stretchable material of Comparative Example 12, the ratio (bymass) of the acrylic resin 1 to the block copolymer 3 in the polymercomposition to form the stretchable material falls within the rangegiven by the relationship (1) and the proportion (by mass) of thesoftener c-1 satisfies the relationship (2). In this stretchablematerial, however, the weight average molecular weight of the blockcopolymer 3 is greater than 200,000, and thus the stretchable materialis less favorable than the stretchable material of Example 21 in termsof the stress relaxation property, the tensile permanent set, and theformability.

[III] Evaluation of Physical Properties of Laminates

In the following Examples and Comparative Examples, laminates wereprepared having a layer formed of the polymer compositions of thepresent invention or their counterparts. The laminates were measured orevaluated for the scratch resistance and the abrasion resistance on theside of the layer of the polymer compositions or their counterparts. Themeasurements and evaluations were performed according to the followingmethods:

m) Scratch Resistance

A 5 cm (width)×11 cm (length)×0.2 cm (thickness) sample piece was madefrom each of the laminates obtained in Examples 22 through 29 andComparative Examples 13 through 19. In the same manner as described inthe section [I] a) above, the laminates were evaluated on the side ofthe layer formed of the polymer compositions of the present invention ortheir counterparts. A sample with a shallower scratch was considered tohave a higher scratch resistance.

n) Abrasion Resistance

A 11 cm (width)×11 cm (length)×0.2 cm (thickness) sample piece was madefrom each of the laminates obtained in Examples 22 through 29 andComparative Examples 13 through 19. In the same manner as described inthe section [I] b) above, Taber abrasion of the laminates were measuredon the side of the layer formed of the polymer compositions of thepresent invention or their counterparts. A sample with a lower abrasionwas considered to have a higher abrasion resistance.

The components used in the following Examples and Comparative Exampleswere prepared as follows:

Components of the Polymer Compositions

(a) Block Copolymer

The block copolymer 1, 3, or 5 described in [I] above.

(b) Acrylic Resin

The acrylic resin 1 described in [I] above.

(c) Softener

The softener c-1 described in [I] above.

Thermoplastic Resins

1. Olefin-Based Thermoplastic Elastomer

-   (MILLASTOMER 7030N (product name), manufactured by Mitsui    Petrochemicals Co., Ltd.)    2. Resin Composition Containing a Styrene-Based Thermoplastic    Elastomer-   (SEPTON COMPOUND CJ-002 (product name), manufactured by Kuraray    Plastics Co., Ltd.)

Using an injection molding machine (IS-55EPN, manufactured by ToshibaMachine Co., Ltd.), each of the thermoplastic resins 1 and 2 was formedinto a 15 cm (length)×15 cm (width)×0.1 cm (thickness) sheet in advancewith the cylinder temperature kept at 230° C. and the mold temperatureat 50° C.

EXAMPLES 22 THROUGH 29 AND COMPARATIVE EXAMPLES 13 THROUGH 19

-   (1) According to the compositions shown in Tables 7 through 10    below, the block copolymer 1, 3 or 5, the acrylic resin 1, and the    softener c-1 were mixed in respective combinations. The components    were premixed together in a Henschel mixer and the resulting mixture    was fed to a twin screw extruder (TEM-35B, manufactured by Toshiba    Machine Co., Ltd.) where it was kneaded at 230° C. and was extruded    into strands. The extruded strands were then cut to form pellets of    the polymer composition.-   (2) Using an injection molding machine (IS-55EPN, manufactured by    Toshiba Machine Co., Ltd.), the pellets of each polymer composition    obtained in (1) above were formed into a 15 cm (length)×15 cm    (width)×0.1 cm (thickness) sheet with the cylinder temperature kept    at 250° C. and the mold temperature at 80° C.-   (3) One of the polymer composition sheets obtained in (2) above was    overlaid with the thermoplastic resin sheet 1 or 2. The overlaid    layers were placed in a 15 cm (length)×15 cm (width)×0.2 cm    (thickness) metal frame and were pressed on a press at 230° C. for 3    minutes under 10 MPa to thermally adhere the two layers to each    other and to thereby form a laminate. In the manner described above,    the laminate so obtained was measured for the scratch resistance and    the abrasion resistance. The results are as shown in Tables 7    through 10 below.

TABLE 7 Example Example Example Example 22 23 24 25 [Polymer composition(part by mass)] Block copolymer 1 70 54 70 54 Acrylic resin 1 30 36 3036 Softener c-1 10 10 [Thermoplastic resin] 1 1 2 2 [Physical property]1.5 1.9 1.3 1.9 Scratch resistance (μm) Taber abrasion (mm³) 29 26 22 24

TABLE 8 Example Example Example Example 26 27 28 29 [Polymer composition(part by mass)] Block copolymer 1 40 36 42 65 Acrylic resin 1 55 54 4320 Softener c-1 5 10 15 15 [Thermoplastic resin] 1 1 1 1 [Physicalproperties] 4.5 4.6 1.8 5.4 Scratch resistance (μm) Taber abrasion (mm³)32 23 8 31

TABLE 9 Comparative Comparative Comparative Comparative Example 13Example 14 Example 15 Example 16 [Polymer composition (part by mass)]Block copolymer 1 30 24 70 27 Acrylic resin 1 70 56 18 Softener c-1 2030 55 [Thermoplastic resin] 1 1 1 1 [Physical properties] 15 19 9.8 20Scratch resistance (μm) Taber abrasion (mm³) 219 234 >500 >500

TABLE 10 Compara- Compara- Compara- tive tive tive Example 17 Example 18Example 19 [Polymer composition (part by mass)] block copolymer 5 70 54block copolymer 3 35 Acrylic resin 1 30 36 23 Softener c-1 10 42[Thermoplastic resin] 1 1 1 [Physical properties] 11.5 12.3 11.6 Scratchresistance (μm) Taber abrasion (mm³) >500 441 248

As shown in Tables 7 through 10 above, each of the polymer compositionsof the present invention contains the block copolymer 1 and the acrylicresin 1 in predetermined proportions so that the relationship (1) holdsand contains the softener c-1 in a predetermined proportion so that therelationship (2) holds. As can be seen from the results, each of thelaminates of Examples 22 through 29, which has its outer layer formed ofone of the polymer compositions of the present invention, exhibitsscratch resistance and abrasion resistance in a well-balanced manner.

In comparison, the outer layer of the laminate of Comparative Example 13is formed of a polymer composition in which the ratio (by mass) of theacrylic resin 1 to the block copolymer 1 lies outside the range given bythe relationship (1). This laminate shows poor scratch resistance andpoor abrasion resistance.

In Comparative Example 14, the outer layer of the laminate is formed ofa polymer composition in which the proportion of the softener c-1satisfies the relationship (2) but the ratio (by mass) of the acrylicresin 1 to the block copolymer 1 lies outside the range given by therelationship (1). This laminate also shows poor scratch resistance andpoor abrasion resistance.

The outer layer of the laminate of Comparative Example 15 is formed of apolymer composition that does not contain the acrylic resin 1, whereasthe outer layer of the laminate of Comparative Example 16 is formed of apolymer composition in which the proportion of the softener c-1 does notsatisfy the relationship (2). In either case, the laminate shows poorscratch resistance and poor abrasion resistance.

In each of Comparative Examples 17 and 18, the outer layer of thelaminate is formed of a polymer composition in which the polymer block Ato form the block copolymer 5 is polystyrene. In either case, thelaminate shows poor scratch resistance and poor abrasion resistance.

In Comparative Example 19, the outer layer of the laminate is formed ofa polymer composition in which the block copolymer 3 to form the polymercomposition has a weight average molecular weight of more then 200,000.This laminate also shows poor scratch resistance and poor abrasionresistance.

[IV] Evaluation of Physical Properties of Foam Compositions and Foams

In the following Examples and Comparative Examples, foam compositionsand foams obtained by foaming the foaming compositions were prepared.The foam compositions were measured or evaluated for the formabilitybefore foaming and the foams were measured or evaluated for each of thescratch resistance, abrasion resistance, heat resistance (e.g.,compression permanent set at 70° C.), flexibility, and expansion ratio.The measurements and evaluations were performed according to thefollowing methods:

o) Scratch Resistance (Scratch Test)

Each of the foam compositions obtained in Examples 30 through 32 andComparative Examples 20 through 24 was loaded in a 5 cm (length)×1 cm(width)×0.2 cm (thickness) metal frame at a predetermined filling ratiothat takes into account the expansion ratio of the foam composition. Thefoam composition was then pressed on a press at 230° C. for 4 minutesunder 10 MPa to form a sample piece. On a frictional wear instrument,the sample piece was rubbed (load=500 g/cm², stroke=120 mm, 20 rpm, 10rounds) with a piece of cotton cloth (Kanakin No. 3) with a 15 mm width,and the degree of scratch formation was visually observed: A circleindicates that little or no scratches were observed; and a crossindicates that apparent scratches were observed.

p) Abrasion Resistance

Each of the foam compositions obtained in Examples 30 through 32 andComparative Examples 20 through 24 was filled into a 15 cm (length)×15cm (width)×0.2 cm (thickness) metal frame at a predetermined fillingratio that takes into account the expansion ratio of the foamcomposition. The foam composition was then pressed on a press at 230° C.for 4 minutes under 10 MPa to form a sample piece. In the same manner asdescribed in section [I] b) above, the sample piece was tested for Taberabrasion. A sample with a lower abrasion was considered to have a higherabrasion resistance.

q) Heat Resistance (Compression Permanent Set at 70° C.)

Each of the foam compositions obtained in Examples 30 through 32 andComparative Examples 20 through 24 was filled into a 15 cm (length)×15cm (width)×0.2 cm (thickness) metal frame at a predetermined fillingratio that takes into account the expansion ratio of the foamcomposition. The foam composition was then pressed on a press at 230° C.for 4 minutes under 10 MPa to form a sample piece. Circular pieces, each29 mm in diameter, were then stamped out from the sheet. Six of themwere stacked and the stack was pressed at 200° C. for 5 minutes under2.19 MPa to give a sample piece. According to JIS K 6262, the samplepiece was held compressed by 25% under 70° C. atmosphere for thesubsequent 22 hours. Subsequently, compression was released and thecompression permanent set (%) was measured. A sample with a smallercompression permanent set was considered to have a higher heatresistance.

r) Flexibility (Hardness)

Each of the foam compositions obtained in Examples 30 through 32 andComparative Examples 20 through 24 was filled into a 15 cm (length)×15cm (width)×0.2 cm (thickness) metal frame at a predetermined fillingratio that takes into account the expansion ratio of the foamcomposition. The foam composition was then pressed on a press at 230° C.for 4 minutes under 10 MPa to form a sample piece. According to JIS K6253, the hardness of the sample piece was measured with a type Adurometer to serve as an index of the flexibility.

s) Formability

In the same manner as described in section [I] h) above, each of thepellets of the compositions of Examples 30 through 32 and ComparativeExamples 20 through 24, to which the blowing agent was not yet added,was measured for the MFR. A pellet with a higher MFR was considered tohave a higher formability.

t) Expansion Ratio

Each of the foam compositions obtained in Examples 30 through 32 andComparative Examples 20 through 24 was filled into a 3 cm (length)×3 cm(width)×0.2 cm (thickness) metal frame at a predetermined filling ratiothat allows the foam composition to expand approximately 1.4 times. Thefoam composition was then pressed on a press at 230° C. for 4 minutesunder 10 MPa to form a sheet-like foam. The density of the resultingfoam was determined and was compared with the density of the foamcomposition prior to foaming. The expansion ratio was determined by thefollowing equation:Expansion ratio (times)=Density of foam composition/Density of foam

The components used in the following Examples and Comparative Exampleswere prepared as follows:

(a) Block Copolymer

The block copolymer 2, 3, 6, or 7 described in [I] above.

(b) Acrylic Resin

The acrylic resin 1 described in [I] above.

(c) Softener

The softener c-1 described in [I] above.

(d) Blowing Agent

d-1: Fineblow BX-037 (Product name) (master batch containingazodicarbonamide, manufactured by Mitsubishi Chemical Co., Ltd.)

EXAMPLES 30 THROUGH 32 AND COMPARATIVE EXAMPLES 20 THROUGH 24

-   (1) According to the compositions shown in Tables 11 through 13, all    of the components except the blowing agent d-1, that is, the block    copolymers 2, 3, 6 or 7, the acrylic resin 1, and the softener c-1,    were mixed in respective combinations. The components were premixed    together in a Henschel mixer and the resulting mixture was fed to a    twin screw extruder (TEM-35B, manufactured by Toshiba Machine Co.,    Ltd.) where it was kneaded at 230° C. for about 3 minutes and was    extruded into strands. The extruded strands were then cut to form    pellets of the polymer composition. The MFR of each composition was    determined as described above and is shown in Tables 11 through 13    below.-   (2) The blowing agent d-1 was then mixed with each of the pellets of    the compositions obtained in (1) above to form a foam composition,    which in turn was filled into a 3 cm (length)×3 cm (width)×0.2 cm    (thickness) metal frame at a predetermined filling ratio that allows    the foam composition to expand approximately 1.4 times. The foam    composition was then pressed on a press at 230° C. for 4 minutes    under 10 MPa to form a sheet-like foam. The expansion ratio of each    of the resulting foams was determined as described above and is    shown in Tables 11 through 13 below.

TABLE 11 Example Example Example 30 31 32 [Composition (part by mass)]Block copolymer 2 52 49 42 Acrylic resin 1 20 21 28 Softener c-1 28 3030 Blowing agent d-1 5 5 5 [Physical properties 6.5 3.9 8.9 beforefoaming] MFR (g/10 min) [Physical properties ∘ ∘ ∘ after foaming]Scratch resistance Taber abrasion (mm³) 35 15 30 Compression permanent30 24 26 set at 70° C. (%) Hardness (Type A) 25 15 10 Expansion ratio(times) 1.42 1.41 1.40

TABLE 12 Comparative Comparative Example 20 Example 21 [Composition(part by mass)] Block copolymer 2 20 27 Acrylic resin 1 50 18 Softenerc-1 30 55 Blowing agent d-1 5 5 [Physical properties before foaming]9.8 >100 MFR (g/10 min) [Physical properties after foaming] x x Scratchresistance Taber abrasion (mm³) 110 >500 Compression permanent set at70° C. (%) 66 20 Hardness (Type A) 30 5 Expansion ratio (times) 1.421.37

TABLE 13 Compara- Compara- Compara- tive tive tive Example ExampleExample 22 23 24 [Composition (blending amount: mass ratio)] Blockcopolymer 7 42 Block copolymer 6 42 Block copolymer 3 42 Acrylic resin 128 28 28 Softener c-1 30 30 30 Blowing agent d-1 5 5 5 [Physicalproperties >100 >100 0.02 before foaming] MFR(g/10 min) [Physicalproperties x ∘ x after foaming] Scratch resistance Taber abrasion(mm³) >500 75 170 Compression permanent 100 100 23 set at 70° C. (%)Hardness (Type A) 20 22 60 Expansion ratio (times) 1.31 1.39 1.15

As shown in Table 11 above, each of the foam compositions of Examples 30through 32 and each of the foams formed of the respective foamcompositions contain the block copolymer 2 and the acrylic resin 1 inpredetermined proportions (by mass) so that the relationship (1) holdsand contain the softener c-1 in a predetermined proportion so that therelationship (2) holds. As can be seen from the results, each of thefoam compositions of Examples 30 through 32 and the foams formed thereofare favorable in terms of scratch resistance, abrasion resistance,compression permanent set at 70° C. (heat resistance), flexibility,formability, and foamability.

In comparison, in the foam composition of Comparative Example 20 and thefoam formed thereof, the ratio (by mass) of the acrylic resin 1 to theblock copolymer 2 lies outside the range given by the relationship (1)although they contain the softener c-1 in a proportion that satisfiesthe relationship (2). The composition and the foam made thereof exhibitgood foamability but are less favorable in terms of scratch resistance,abrasion resistance and compression permanent set at 70° C. (heatresistance).

In the foam composition of Comparative Example 21 and the foam formedthereof, the ratio (by mass) of the acrylic resin 1 to the blockcopolymer 2 falls within the range given by the relationship (1), butthe proportion (by mass) of the softener c-1 does not satisfy therelationship (2). The foam composition and the foam formed thereof showpoor scratch resistance and poor abrasion resistance.

In the foam composition of Comparative Example 22 and the foam formedthereof, the ratio (by mass) of the acrylic resin 1 to the blockcopolymer 7 falls within the range given by the relationship (1) and theproportion (by mass) of the softener c-1 satisfies the relationship (2).In this foam composition, however, the polymer block A to form the blockcopolymer 7 is polystyrene, and thus the foam composition and the foamformed thereof are less favorable in terms of scratch resistance,abrasion resistance, and compression permanent set at 70° C. (heatresistance).

In the foam composition of Comparative Example 23 and the foam formedthereof, the ratio (by mass) of the acrylic resin 1 to the blockcopolymer 6 falls within the range given by the relationship (1) and theproportion (by mass) of the softener c-1 satisfies the relationship (2).In this foam composition, however, the weight average molecular weightof the block copolymer 6 is less than 30,000, and thus the foamcomposition and the foam formed thereof exhibit poor compressionpermanent set at 70° C. (heat resistance), though they show foamability,scratch resistance, and abrasion resistance in a well-balanced manner.

In the foam composition of Comparative Example 24 and the foam formedthereof, the ratio (by mass) of the acrylic resin 1 to the blockcopolymer 3 falls within the range given by the relationship (1) and theproportion (by mass) of the softener c-1 satisfies the relationship (2).In this foam composition, however, the weight average molecular weightof the block copolymer 3 is larger than 200,000, and thus the foamcomposition and the foam formed thereof are less favorable in terms ofscratch resistance and abrasion resistance though they show superiorcompression permanent set at 70° C. (heat resistance). They also lackproper foamability. For this reason, more foam composition must beintroduced into the metal frame than in the other Examples to obtain thesheet foam with the size of the metal frame.

INDUSTRIAL APPLICABILITY

The present invention provides a polymer composition that not only showsgood formability, flexibility, rubber elasticity, mechanical strength,and transparency, but also exhibits a scratch resistance and abrasionresistance comparable to those of polyurethane-based thermoplasticelastomers or polyester-based thermoplastic elastomers. By exploitingthese favorable characteristics, the polymer composition of the presentinvention can be effectively used in a wide range of applications,including stretchable materials, laminates, and foams.

1. A polymer composition, comprising: a block copolymer (a) comprising apolymer block A, which comprises mainly an α-methylstyrene, and ahydrogenated or unhydrogenated polymer block B, which comprises aconjugated diene, wherein block copolymer (a) has a weight averagemolecular weight of 30,000 to 200,000; an acrylic resin (b) which is ahomopolymer of methyl methacrylate or a copolymer comprising methylmethacrylate as the major component and copolymerizable monomersselected from the group consisting of (meth)acrylic acid, metal salts of(meth)acrylic acid, (meth)acrylic acid esters, vinyl acetate, aromaticvinyl compounds, maleic anhydride, maleimide compounds and mixturesthereof; and optionally, a softener (c); and wherein proportions (bymass) of respective components in the polymer composition are such thateach of the following relationships (1) and (2) holds:0.05<Wb/Wa<2  (1) andWc/(Wa+Wb+Wc)<0.5  (2) wherein Wa, Wb, and Wc represent the amounts (bymass) of the block copolymer (a), the acrylic resin (b) and the softener(c), respectively, and wherein the polymer composition has a morphologyin which the block copolymer (a) forms a continuous phase (matrix) andthe acrylic resin (b) forms particles having an average particle size of0.2 μm or less, that are dispersed throughout the continuous phase,forming sea-island structures.
 2. The polymer composition according toclaim 1, wherein the block copolymer (a) comprises: (1) a polymer blockA comprising mainly an α-methylstyrene and having a weight averagemolecular weight of 1,000 to 50,000; and (2) a polymer block B includinga block b1 that has a weight average molecular weight of 1,000 to30,000, and in which less than 30% of the conjugated diene units toconstitute the block are linked via 1,4-linkages, and a block b2 thathas a weight average molecular weight of 25,000 to 190,000, and in which30% or more of the conjugated diene units to constitute the block arelinked via 1,4-linkages; and wherein the block copolymer (a) includes atleast one A-b1-b2 structure.
 3. A stretchable material, comprising: thepolymer composition according to claim
 1. 4. The stretchable materialaccording to claim 3, wherein the stretchable material is provided inthe form of a film, strand, band, or nonwoven fabric comprising thepolymer composition.
 5. The stretchable material according to claim 3,wherein the stretchable material yields a 0.8 MPa or larger stress whenformed into a 1 mm thick, No.2 dumbbell-molded sample piece, accordingto JIS K 6251, and stretched by 50% at a test speed of 20 mm/min at 25°C., with the grip distance of 70 mm, and gives a 50% or higher stressretention after held under the conditions for 2 hours.
 6. A laminate,comprising: a layer comprising the polymer composition according toclaim 1, and a layer comprising a different material.
 7. The laminateaccording to claim 6, wherein the different material is a thermoplasticresin.
 8. The laminate according to claim 7, wherein the differentmaterial comprises at least one thermoplastic resin selected from thegroup consisting of olefin-based resin, olefin-based thermoplasticelastomer, styrene-based thermoplastic elastomer, and a resincomposition containing a styrene-based thermoplastic elastomer.
 9. Alaminate, comprising: an outermost layer comprising the polymercomposition according to claim 1, and a layer comprising a differentmaterial.
 10. A foam composition, comprising: the polymer compositionaccording to claim 1, and a blowing agent (d), and wherein the blowingagent (d) is contained in a proportion (by mass), such that thefollowing relationship (3) holds:0.01<Wd/(Wa+Wb+Wc)<0.1  (3) wherein Wa, Wb, Wc, and Wd represent theamounts (by mass) of the block copolymer (a), the acrylic resin (b), thesoftener (c), and the blowing agent (d) that together form the foamcomposition, respectively.
 11. A foam obtained by foaming the foamcomposition according to claim
 10. 12. A stretchable material,comprising: the polymer composition according to claim
 2. 13. Alaminate, comprising: a layer comprising the polymer compositionaccording to claim 2, and a layer comprising a different material.
 14. Alaminate, comprising: an outermost layer comprising the polymercomposition according to claim 2, and a layer comprising a differentmaterial.
 15. A foam composition, comprising: the polymer compositionaccording to claim 2, and a blowing agent (d), and wherein the blowingagent (d) is contained in a proportion (by mass), such that thefollowing relationship (3) holds:0.01<Wd/(Wa+Wb+Wc)<0.1  (3) wherein Wa, Wb, Wc, and Wd represent theamounts (by mass) of the block copolymer (a), the acrylic resin (b), thesoftener (c), and the blowing agent (d) that together form the foamcomposition, respectively.
 16. The polymer composition according toclaim 1, wherein the acrylic resin (b) is a copolymer comprising methylmethacrylate and methyl acrylate.
 17. The polymer composition accordingto claim 2, wherein the acrylic resin (b) is a copolymer comprisingmethyl methacrylate and methyl acrylate.